Cook spaghetti according to pkg directions. Meanwhile, in a large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Stir in spaghetti sauce and seasoned salt; set aside. In a large bowl, whisk the eggs, Parmesan cheese and butter. Drain spaghetti; add to egg mixture and toss to coat. 

Place half of the spaghetti mixture in a greased 13x9-in. or 3-qt. baking dish. Top with half of the cottage cheese, meat sauce and Mozzarella cheese. Repeat layers. Cover and bake at 350° for 40 minutes. Uncover; bake until cheese is melted, 20-25 minutes longer.