Saute onions in melted butter in large saucepan until translucent. Add sausage and cook until brown. Place onions and sausage on plate, slice each link into 4 or 5 pieces, and set aside. Brown ground beef. Add sausage and onion to browned ground beef. Add seasonings, corn, tomato sauce, and milk. Simmer 20 minutes. Stir corn muffin mix into meat mixture. Pour into 9x13 baking dish. Top with cheese. Bake at 325 for 40 minutes.