In a large skillet, cook onion and ground beef over medium heat. Add spaghetti sauce, and simmer for 15 minutes.
In a lightly greased 9x13 inch baking dish layer the following: ½ of the pasta, provolone cheese, sour cream, ½ sauce mixture, remaining ziti, mozzarella cheese and remaining sauce mixture. Top with grated Parmesan cheese.
Bake for 30 minutes or until cheese is melted.
Recipe by Eighteen25 at https://eighteen25.com/baked-ziti-recipe/