Baked Ziti

1 box ziti pasta
1 onion, chopped
1 lb ground beef or turkey
2 (26 ounce) jars spaghetti sauce
6 ounces provolone cheese, sliced
1 1/2 c sour cream
6 ounces mozzarella cheese, shredded
2 T 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 inch
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.