4 Cups Shredded Mozzarella Cheese, ( 1 Cup Reserved)
Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9×13-inch baking dish.
Bring a large pot of lightly salted water to a boil. Cook spaghetti in boiling water, stirring occasionally until cooked through but firm to the bite, about 12 minutes. Drain.
Heat a large skillet over medium heat; cook and stir beef, sausage and onion until meat is browned and onions are soft and translucent, about 10 minutes. Drain. Stir in spaghetti sauce and seasoned salt.
Whisk eggs, Parmesan cheese, and butter in a large bowl. Mix in spaghetti noodles to egg mixture and toss to coat. Place the spaghetti mixture into a large mixing bowl, fold in the ricotta cheese, mozzarella, and meat sauce. Mix well until combined. Pour all into the prepared 9×13-inch baking dish. Top with remaining Mozzarella. Cover with aluminum foil sprayed with oil.
Bake in preheated oven for 40 minutes. Remove foil and continue to bake until the cheese is melted and lightly browned, 20 to 25 minutes longer.
Serve with Mediterranean salad with lemon vinaigrette and garlic toast.