Cook spaghetti according to package directions; drain. Add butter and Parmesan; toss to coat.
Process the ricotta cheese in a blender until smooth. In a large bowl, combine spaghetti sauce with ricotta; stir in onion, garlic, basil, oregano and half of the mozzarella. Add the spaghetti; toss to coat.
Transfer to a 13x9 baking dish coated with cooking spray. Sprinkle with the remaining mozzarella.
Cover; bake at 350° for 40-45 minutes or until heated through.