Caramelized Onion Tart with Gruyere

Caramelized Onion Tart on a wooden cutting board.

Caramelized Onion Tart with Gruyere

Caramelized Onion Tart with Bacon and Gruyere Cheese and. Simply seasoned with fresh thyme and balsamic vinegar, This creamy cheese tart is a winner.

Course Appetizer Recipes

Cuisine French

Prep Time 15

Cook Time 1 15

Total Time 1 30

Servings slices

Calories 319kcal

Author Lea Ann Brown

Ingredients

1 Pie Crust preferably homemade - blind baked
6 ounces bacon cut into ½ inch lardons
4 large onions peeled and cut into ¼ inch slices
1 tablespoon sugar
½ teaspoon Kosher salt
1 ½ Tablespoon balsamic vinegar
1 tablespoon fresh thyme chopped, or one teaspoon of dried thyme
¼ teaspoon freshly ground black pepper
¼ cup heavy cream
1 cup grated gruyere cheese

Instructions

Prepare Blind Baked Pie Crust. You'll find complete instructions in my Pie Crust Article.
Cook The Bacon: Cut the bacon into lardons and cook it in a large frying pan, stirring often, until cooked and lightly crisp. About 15 minutes. Transfer the bacon to a plate and leave about two tablespoons of the rendered fat in the pan. The bacon fat becomes the cooking fat for the onions, carrying its savory flavor into the filling.
Prepare the Onions: In the meantime, cut the ends off each onion, remove skin and slice into ¼ inch rounds.
Caramelize the Onions: Reduce the heat to medium-low. Add the onions, sugar and salt to the reserved bacon fat. Stir frequently as the onions soften and cook down to about one-third of their original volume, approximately 30 minutes. If the bacon hasn't produced enough fat, add a generous tablespoon of butter.
Add the Balsamic Vinegar: Add the balsamic vinegar, reduce the heat to low, and continue cooking for about 15 minutes, until the onions are evenly golden brown and softened. Stir frequently and scrape up the browned bits from the bottom of the pan. Watch the onions carefully: the goal is soft, golden, caramelized onions, not burned edges. Lea Ann's tip: Don't rush this step by turning up the heat. Give the onions time to soften and develop their flavor. Slice them evenly, keep the heat low enough to prevent scorching, and use their color and texture as your guide.
Finish the onion filling: Remove the pan from the heat. Stir in the thyme, freshly ground black pepper and cooked bacon. Allow the mixture to cool slightly, then stir in the heavy cream until everything is thoroughly combined. The filling is now ready for the prepared tart shell.
Fill the blind-baked tart shell: Preheat the oven to 350°F. Place the onion filling in the 8-inch blind-baked tart shell. Spread it evenly with the back of a spoon so the filling reaches the edges.
Add the Gruyere Cheese. Sprinkle the grated Gruyère evenly over the onion filling.
Bake the tart: Place the tart on a baking sheet and bake at 350°F for about 15 minutes, until the filling is set. Allow the tart to settle briefly before removing it from the pan. Serve warm or at room temperature, garnished with a sprig of thyme.
Serve warm or at room temperature. Garnish with a sprig of thyme.

Video

Notes

Cooking times and prep do not reflect any time spent on the pie crust.

Tips For Success

Don't rush the onions: Allow at least 45 minutes for the onion-cooking process in this recipe. The onions should soften, reduce substantially in volume and become evenly golden. Keep the heat low enough to prevent burning, and stir frequently.
Why blind-bake the tart shell? Blind baking means baking the pastry shell before adding the filling. Because the onions are already cooked and the tart needs only a short final bake, the pastry must be cooked beforehand. Otherwise, the crust may not bake through before the filling is ready.
Use a baking sheet: Place the filled tart pan on a baking sheet before transferring it to the oven. Tart pans typically have removable bottoms, and the baking sheet makes the tart easier to move without disturbing the base.
Choose the right tart pan: An 8-inch tart pan is recommended for this recipe. A 9-inch pan also works, but the filling will be thinner. You can also divide the filling among individual 4- to 5-inch tartlet pans.

Nutrition