Brown beef, sausage and onion in a skillet over medium heat; drain. Stir in sauce; reduce heat to low ad simmer 15 minutes.
Layer in a greased 13"x9" baking pan as follows: half the pasta, provolone cheese, sour cream, half the sauce mixture, remaining pasta, mozzarella cheese and remaining sauce.
Top with parmesan cheese. Cover and bake at 350° for 30 minutes or until hot, bubbly and cheeses are melted.