Bring a large pot of salted water to a boil and cook pasta according to package instructions until al dente.
Before draining, reserve ½ cup of pasta water. Drain pasta and set aside.
In a large skillet, heat olive oil over medium heat.
Add minced garlic and saute for 30 seconds to 1 minute until fragrant.
Add chopped spinach and cook for 1-2 minutes, stirring until wilted.
In a large mixing bowl, whisk together ricotta cheese, lemon zest, lemon juice, Parmesan cheese, salt, black pepper, and red pepper flakes.
Slowly stir in ¼ cup of the reserved pasta water to loosen the sauce. Add more if needed for a creamy texture.
Add the cooked pasta to the skillet with spinach and garlic.
Pour the ricotta-lemon sauce over the pasta and toss to coat evenly.
If the sauce is too thick, add a little more reserved pasta water until desired consistency is reached.
Plate the pasta and top with fresh basil or parsley.
Sprinkle with toasted pine nuts or walnuts for added crunch.
Serve warm with extra Parmesan cheese on top.
