Cook spaghetti according to package directions and drain. Return to the pot, then set aside.
In a large bowl, whisk the eggs, Parmesan cheese and butter. Add mixture to the spaghetti pot and toss to coat.
In a large skillet, cook beef, onion, and garlic over medium heat until meat is no longer pink. Drain the fat, return to pan then stir in the spaghetti sauce, salt, and Italian seasoning.
Place half of the spaghetti mixture in a greased 9x13 baking dish. Top with half of the ricotta cheese, meat sauce and mozzarella cheese. Repeat layers.
Cover with foil and bake at 350° for 20 minutes.
Uncover and bake for 10 minutes or until the cheese is melted.