Bring a large pot of salted water to boil. Add pasta and cook according to instructions - about 8 min. Drain.
At the same time, in a large skillet, brown onion and ground beef over medium heat. Add spaghetti sauce and Pasta Sprinkle and simmer for 15 min.
Preheat the oven to 350*. Grease a 9x13 in. baking dish.
Layer ingredients in dish as follows: 1/2 of cooked ziti, Provolone cheese, sour cream, 1/2 sauce mixture, remaining cooked ziti, mozzarella cheese, remaining sauce mixture. Top with an appropriate amount of parmesan cheese.
Bake for 30 minutes until cheese melts