1.Cook pasta according to package directions. Drain, reserving 3/4 cup pasta water.
2.While pasta is cooking, in a separate bowl, thoroughly combine ricotta, lemon juice and rind, 1/4 teaspoon salt, black pepper and crushed red pepper. (I listed 1/8 tsp of crushed red pepper, but don't be shy, this dish is even better with a bit of a kick from the red pepper, so adjust according to your taste level ).
3.Heat oil in a large skillet over medium-high heat. Add bell pepper and garlic, saute for 3 minutes.
4.Add pasta, spinach, ricotta mixture and pasta water to skillet; cook about 1 minute or until spinach wilts. Top with extra salt, black pepper and crushed red pepper if desired.