Baked Ziti

1 pound ziti or penne pasta, cooked al dente

1 onion, chopped
1 lb Italian Sausage or ground beef
2 (26 oz) jars spaghetti sauce
6 ounces sliced provolone cheese
1 1/2 cups sour cream
1 1/2 cups shredded mozarella cheese
2 TBsp grated fresh parmesan cheese

In a large skillet, brown onion and meat over medium heat. Drain excess fat. Add spaghetti sauce and simmer about 15 minutes. In a greased 9x13 baking dish, layer half of the ziti, half of the sauce, provolone chease and sour cream. Top with remaining ziti, remaining sauce, mozarella cheese, and parm cheese. Bake uncovered at 350 degrees for 30 minutes.