Place tomatoes in a 9×13 pan and drizzle with ½ tablespoon olive oil. Salt and pepper. Set aside.
Heat remaining 1½ tablespoons oil in a skillet over medium heat. Saute onion until translucent and soft. Add the garlic and spinach and cook until wilted. Season with salt and pepper to taste.
Mix ricotta and Parmesan together. Add in the spinach mixture and stuff into peppers. Sprinkle with more Parmesan cheese and arrange in the pan with the tomatoes.
Bake for 25-30 minutes or until lightly browned. Garnish with more Parmesan and some fresh parsley or basil.
Serve over rice, orzo, or quinoa.