Cook egg noodles as directed on package. Drain well.
Meanwhile, brown ground beef and onion in large skillet on medium-high heat. Drain fat. Add tomato sauce, spaghetti sauce mix and water; stir until well blended. Bring to boil. Reduce heat to low; cover and simmer 10 minutes.
Stir in egg noodles. Sprinkle with cheese; cover. Cook 5 minutes on low heat or until cheese is melted.