Preheat oven to 350°. Cook spaghetti according to package directions for al dente. Meanwhile, in a large skillet, cook beef and onion over medium heat until beef is no longer pink and onion is tender, 6-8 minutes, breaking up beef into crumbles; drain. Stir in pasta 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. Place baking dish on a rimmed baking sheet., Cover and bake for 40 minutes. Uncover; bake until cheese is melted, 20-25 minutes longer. Let stand 15 minutes before serving. If desired, sprinkle with basil.