This Caramelized Onion Tart with Gruyere Cheese is a Heavenly combination of sweet and savory. With balsamic vinegar, bacon, cream and thyme … who can resist. This Savory French tart is perfect for an appetizer or a cozy light dinner served with a tossed salad.
It’s late July in Colorado and that means I’m more excited to cook than any other time of year. Our famous Palisade Peaches are starting to come in, fresh sweet corn and Rocky Ford Melons are here, and its nearing Pueblo Chile Season.
When our Colorado grown onions hit our markets, I can’t think of a better way to use them than in this caramelized onion tart.
There’s so much to love. Caramelized onions become even tastier with the addition bacon, balsamic vinegar and cream. It’s almost like having a bowl of French Onion Soup in a flaky crust.
This caramelized onion tart can be made ahead, or served warm. It’s a lovely addition to a wine tasting party, an appetizer for a special dinner, or as a main course.
This onion tart recipe comes from the Pastry Kitchen at Cook Street Culinary School, where we made it several times during my time spent there.
Ingredients You’ll Need
- One pie crust to make an 8-inch tart shell.
- Sweet Onions or yellow onions.
- Bacon
- Cream
- Gruyere Cheese
- Balsamic Vinegar
- Dried Thyme
- Sugar
- Salt and Pepper
Ingredient Substitutes
- Cheese: Good substitutes for Gruyere are, Emmental, American Swiss Cheese, Comte, Fontina and Jarlsberg. Jarlsberg would be my first choice. Many caramelized onion tarts are made with goat cheese. Many don’t like the tart flavor of the goat cheese with sweet onions.
- Thyme: You most certainly can substitute fresh thyme for dried. And fresh thyme makes a nice garnish for the tart.
- Vinegar: Please no substitutes here. Balsamic is a unique, rich flavored vinegar that is important to the over all flavor of this Caramelized Onion Tart.
Pro Tip: When substituting dried herbs for fresh, a good rule of thumb is 1 Tablespoon of fresh herbs = 1 teaspoon dried herbs. Some herbs season better when used in dried form. Oregano is a good example.
Step by Step Instructions
- Step 1: Cook The Bacon: Cut the bacon into ½ lardons and cook in a large fry pan, stirring often until soft crispy. Remove bacon to a plate and discard all but about two tablespoon of the grease.
- Step 2: Prepare the Onions: In the meantime, cut the ends of each onion, remove skin and slice into ¼ inch rounds.
- Step 3: Caramelize the Onions: Reduce heat medium low. Add the onions, sugar and salt and cook, stirring often until they cook down by two thirds, about 30 minutes. Add a generous 1 tablespoon pat of butter if you feel the bacon didn’t yield enough grease. Add the balsamic vinegar, reduce heat to low, and continue to cook until the onions are an even golden brown and softened, 15 more minutes.
- Step 4: Add the Cream: Remove from heat, stir in the thyme, black pepper and cooked bacon. Allow the ingredients to cool slightly. Stir the cream into the caramelized onions until thoroughly combined.
- Step 5: Fill The Pie Shell: Place the filling in the 8″ blind baked tart shell and spread it evenly with the back of a spoon.
- Step 6: Add the Gruyere Cheese. Sprinkle grated Gruyere Cheese on top.
- Step 7: Bake the tart: Bake in a 350 degree oven until the filling is set, about 15 minutes.
FAQ’s
An 8″ tart pan is recommended for this recipe. You can use a 9″ pan, but please know that the filling will be thinner. Four – Five inch individual tartlet pans are a fun way to serve this Caramelized Onion Tart.
You can, but the end result will be far superior if you use a homemade tart shell.
Yes, and that’s a very smart way to make this. Blind bake the crust up to two days in advance. When ready to prepare, assemble the tart and let it sit in the refrigerator until ready to bake. This tart can also be baked a couple hours ahead of when you’re planning on serving it. Cover with plastic wrap, or place it on a cake stand until serving time. No need to refrigerate if serving within a couple of hours, and it works well at room temperature.
Tips For Success
- Don’t rush the onions. It will take at least 45 minutes for them to be golden and caramelized. And don’t cook them on a higher heat. The lowest setting on the burner will create the best results.
- Slice the onions evenly so they’ll all cook the same.
- You MUST use a pie shell that has been cooked, this is called a Blind Baked Pie Shell. When making pies or tarts that call for a filling that’s already been cooked, you’ll need to blind bake the shell first. Which simply means to pre-cook the dough before adding the filling. That’s because the hour or so cooking time that it takes to bake a pie crust would over-cook the fillings, such as in this Caramelized Onion Tart Filling. This filling is already cooked, and simply needs to “set up” with a short baking time.
- Use A Homemade Pie Crust: I hope you’ll consider taking the time to make a homemade pie shell for this tart recipe. One of the great take-aways from Culinary School was how to make an All Butter Pie Crust. It’s really very easy and a skill I feel every home cook should learn. As French technique you’ll also see it referred to as pate brisee.
- Please reference my article on making a homemade pie crust for the recipe and instructions on blind baking.
- Place tart on a baking sheet to bake. Tart pans have a removable bottom. Using a sheet pan makes it easier to get it in and take it out of the oven, without disturbing that removable disk.
Leftovers and Storage
- Store cooled leftovers in a sealed container in the refrigerator for 4 – 5 days. A zip-lock bag works well here.
- You can also freeze any left over slices in a freezer safe container for up to 3 months.
- Let the tart come to room temperature to eat, or gently re-heat in the microwave or a 300 degree oven. Reheating a slice in an air-fryer keeps the crust nice and crispy.
Recipe For Caramelized Onion Tart
This caramelized onion tart recipe is delightful with flavors and textures. It’s a great appetizer to serve at a wine tasting party, or even as a starter for a special meal.
The rich, sweet aroma of slowly caramelized onions, paired with the buttery, flaky crust, creates a balance that is both comforting and sophisticated.
Whether served as an impressive appetizer at a dinner party or enjoyed as a savory treat for a cozy night in, this tart is sure to leave a lasting impression.
This caramelized onion tart is a versatile and timeless addition to any home cook’s collection. So, roll up your sleeves, embrace the art of caramelization. Cheers to creating unforgettable moments around the table with this exceptional caramelized onion tart!
More Popular Tart Recipes
We made a lot of tarts in Culinary School. Fun and rewarding, take a look at these.
And if you’re looking for more impressive appetizer ideas, don’t miss my Appetizer Category, you’ll find lots of fun recipes, including this very popular Smoked Salmon Platter.
If you liked this recipe, please leave a star ⭐⭐⭐⭐⭐ rating in the recipe card below and leave a comment. I always appreciate your feedback and hearing how everything went.
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Caramelized Onion Tart with Gruyere
Ingredients
- 1 Pie Crust preferably homemade – blind baked
- 6 ounces bacon chopped and cooked (about 4-5 slices)
- 4 large onions cut into ¼ inch slices
- 1 tablespoon sugar
- ½ teaspoon Kosher salt
- 1 ½ Tablespoon balsamic vinegar
- 2 tablespoons fresh thyme chopped, or two teaspoons of dried thyme
- ¼ teaspoon freshly ground black pepper
- ¼ cup heavy cream
- 1 cup gruyere grated
Instructions
- Prepare Blind Baked Pie Crust. You'll find complete instructions in my Pie Crust Article.
- Cut the bacon into ½ lardons and cook in a large fry pan, stirring often until soft crispy. Remove bacon to a plate and discard all but about 2 tablespoons of the grease.
- In the meantime, cut the ends of each onion, remove skin and slice into ¼ inch rounds. Reduce heat medium low. Add the onions, sugar and salt and cook, stirring often until they cook down by two thirds, about 30 minutes. Add a generous 1 tablespoon pat of butter if you feel the bacon didn't yield enough grease. (I always do anyway)
- Add the balsamic vinegar, reduce heat to low, and continue to cook until the onions are an even golden brown and softened, 15 minutes.
- Stir often and scrape up any brown bits clinging to the bottom of the pan. while the onions cook, watch them closely, you don't want them to burn, just to become golden and caramelized.
- Remove from heat, stir in the thyme, black pepper and cooked bacon. Allow the ingredients to cool slightly. Stir the cream into the caramelized onions until thoroughly combined.
- Preheat oven to 350 degrees.
- Place the filling in the 8" blind baked tart shell and spread it evenly with the back of a spoon. Sprinkle grated gruyere on top. Bake in oven until the filling is set, about 15 minutes.
- Serve warm or at room temperature. Garnish with a sprig of thyme.
Video
Notes
-
- Don’t rush the onions. It will take at least 45 minutes for them to be golden and caramelized. And don’t cook them on a higher heat. The lowest setting on the burner will create the best results. And slice them evenly for even cooking.
-
- You MUST use a pie shell that has been cooked, this is called a Blind Baked Pie Shell. When making pies or tarts that call for a filling that’s already been cooked, you’ll need to blind bake the shell first. Which simply means to pre-cook the dough before adding the filling. That’s because the hour or so cooking time that it takes to bake a pie crust would over-cook the fillings, such as in this Caramelized Onion Tart Filling. It’s already cooked, and simply needs to “set up” with a short baking time.
-
- Use A Homemade Pie Crust: I hope you’ll consider taking the time to make a homemade pie shell for this tart recipe. One of the great take-aways from Culinary School was how to make an All Butter Pie Crust. It’s really very easy and a skill I feel every home cook should learn. As French technique you’ll also see it referred to as pate brisee.
-
- Please reference my article on making a homemade pie crust for the recipe and instructions on blind baking.
- Place tart on a baking sheet to bake. Tart pans have a removable bottom. Using a sheet pan makes it easier to get it in and take it out of the oven, without disturbing the removable disk
Nutrition
Caramelized Onion Tart … It’s What’s For Dinner
Why Trust These Recipes? Lea Ann Brown has lived, worked and played in Colorado for 45 years. She has immersed herself in the Colorado Culinary space, is a Culinary School Graduate and publishes her Colorado food Blog, Cooking On The Ranch.
I’ve been asked to bring an appetizer to a dinner we have been invited to and I think this will be perfect.
Always looking for dishes that I could have for a quick lunch that don’t involve a ton of protein. This was so delicious tonight at dinner. I’m hoping that it will hold over well for tomorrow’s lunch. Lots of flavor and everything just works so well together.
Making this for the second time (last Sunday was first). It is perfection and I plan to eat lots of tarts when we’re in France next month.
I am going to make this. About how many slices of bacon will yield the 3 ounces
Thanks for your note Lisa. About 3 – 4 slices. I do recommend using a kitchen scale to weigh. I don’t know how I live without mine. Let me know if you have any other questions.
This recipe was SO delightfully delicious! I have made it twice now, and both times got rave reviews! The second time, I added garlic and it was amazing! Will definitely make again and again! LOVE this recipe!
Made this for a ladies luncheon. Absolutely the hit of the day! Easy to make, simple ingredients and a bang up result. Looked like a million bucks and tasted as such as well. Thanks for sharing.
Hi Donna
I am so glad you made and liked the tart. And that it was a ht at the ladies luncheon. How fun!
I appreciate that you took the time to send a note.
Make it a delicious day.
Made this year this weekend for a friend’s birthday. I also used the dough recipe. It was a great hit!
Hi Morgan! Fabulous. Thanks for letting me know.
Hi Morgan, I’m thrilled that you liked the recipe. Thanks for taking the time to comment.
I made this Wednesday and it was perfect. I found this recipe while looking for recipes I could use with a store bought pie crust. I will try your recipe in the future along with the mini tarts using crescent rolls.
We loved this tart and followed the recipe as written. Thank you!!
Good Morning Kira and Happy Friday.
Thank you so much for your lovely note. I’m so glad you liked the recipe and thank you for taking the time to give it a review.
It’s been awhile since I’ve made this recipe, you’ve inspired me to make it for a weekend treat.
Looks delicious! Any thoughts on whether this would freeze well?
Thanks for sharing! Does it keep long?
This look so good! What a flavorful and filling appetizer to make!
Hi Suzanne and thanks so much for your note. Always love hearing from my readers.
I love making this for our neighborhood wine tasting parties. I’m always asked for the recipe.
I loved this tart the only thing I added was about 1 tablespoon of butter to the onions so they would carmalize a little more and reduced the thyme to 1 tbsp as my husband is not a big fan of it. It was perfect I would make it again with the added butter and only 1 tbsp of fresh thyme. Thx
I .made these as small bites using pillsbury crescent dough in a mini cupcake pan. They turned out good, but the thyme is overpowering and I used less than 1 tablespoon, the recipe calls for 2 so I’m glad I did less. Next time I’ll probably do even less. Thanks for the recipe!
Hi Kristy. I adore that you made these as a mini version. So creative. I have one question to ask – did you use dried thyme or fresh?
I just saw Colorado corn in our grocery store, and was so exited — love the stuff! Way better than the local corn, at least most of it. Anyway, wonderful looking dish. Great appetizer. Heck, I’d eat it as the main course! 🙂
I love onions, I love caramelized onions, I love a good pie crust, I love Gruyere cheese so I’m pretty sure I’d really enjoy this although I’d probably use a stronger onion for more onion flavor and a little less sweet