Boil pasa according to directions. Drain. In a large skillet, brown the onion and ground beef. Add spaghetti sauce, and simmer 15 minutes.
Grease 9x13 baking dish. Layer as follows: ½ of ziti, provolone cheese, sour cream, ½ sauce mixture, remaining ziti, mozzarella cheese and remaining sauce mixture. Top with grated parmesan cheese. Cover and Freeze. To prepare – thaw to room temperature. Bake uncovered at 350 for 30 - 40 minutes of until cheeses are melted. Allow to stand for 15 minutes before serving.