Baked Ziti

6 ounces dry ziti pasta
3/8 onion, chopped
6 ounces lean ground beef
1 26 ounce jar spaghetti sauce
2 1/2 ounces provolone cheese, sliced
1/2 cup and 1 tbsp and 2 tsp sour cream
2 1/2 ounces mozzarella cheese, shredded
2 1/2 teaspoons grated Parmesan cheese

Bring a large pot of lightly salted water to a boil.
Add ziti pasta, and cook until al dente, about 8 minutes; drain.
In a large skillet, brown onion and ground beef over medium heat.
Add spaghetti sauce, and simmer 15 minutes.
Preheat the oven to 350 degrees. Butter a 9x13 baking dish.
Layer as follows; 1/2 of the ziti, Provolone cheese, sour cream, 1/2 sauce mixture, remaining ziti, mozzarella cheese and
remaining sauce mixture. Top with grated Parmesan cheese.
Bake for 30 minutes in the preheated oven, or until cheeses are melted. Serves 4