In a large skillet pan, cook beef over medium heat until no longer pink, add onion into the beef, cook for 2 minutes to soften/fry the onion.
In a greased 2 1/2 quart baking dish, layer a third of the spaghetti sauce, half of the pasta and beef, spread 1/2 cup of the cheese over. Repeat layer one more time.
Cover and bake at 400 degrees for 40-45 minutes or until heated through.
Yields about 6-8 servings.