Spinach and Shrimp Fra Diavolo

In a large skillet, heat oil over medium-high heat. Add onion; cook and stir until tender, 5-7 minutes. Add garlic and pepper flakes; cook 1 minute longer. Stir in wine. Bring to a boil; cook until liquid is reduced by half. Stir in tomatoes, tomato sauce, basil, oregano, salt and pepper. Cook and stir until sauce is slightly thickened, about 10 minutes., Add shrimp and spinach; cook and stir until shrimp turn pink and spinach is wilted, 3-5 minutes. If desired, sprinkle with cheese.