Bring a large pot of water to boil, adding salt to taste. Add the ziti pasta and cook about 8 minutes. Drain thoroughly.
Brown onion and ground beef over medium heat in a large skillet. Add spaghetti sauce and simmer for 15 minutes.
Preheat oven to 350 degrees F (175 degrees C). Grease a 9×13 inch baking dish.
Place 1/2 of ziti in bottom of dish and layer with the provolone cheese, sour cream and 1/2 the sauce mixture. Add the other 1/2 of the ziti, the mozzarella cheese and the remaining sauce mixture. Top with grated parmesan cheese.