Spray a stovetop grill pan over medium high heat and spray with cooking spray. Half the lemon and place flesh side down on the hot pan. Sear until nice and charred.
Heat butter in large skillet over medium heat. Add flour and cook for about a minute, stirring constantly to make a roux. Add wine and chicken broth and stir to mix well. Add anchovies. Using wooden spoon, simultaneously stir and mash them until they “dissolve” into the roux.
Add capers and cook a few minutes longer, stirring constantly. If mixture gets too thick, add more wine or chicken broth. You want a thin gravy consistency. Squeeze the lemons and add as much juice as you can into the sauce.
Immediately add spinach, tossing continuously until it wilts.
Reduce heat to low and keep warm.
In the mean time cook fettuccini according to package directions. Drain. In a large serving bowl, toss the pasta with the lemon sauce. Top with grated Parmesan cheese and serve.
Notes
This is not very good the next day. I had some of the leftovers for lunch the next day and the pasta really intensifies over night with a salty strong flavor from the anchovies.