Bring a large pot of lightly salted water to a boil. Add ziti pasta, and cook until al dente, about 8 minutes; drain. Set aside.
In a large saute pan, heat olive oil. Add onion and saute 4 to 5 minutes until translucent. Add ground beef and brown over medium-high heat. Add marinara sauce, cover, and simmer 15 minutes.
Preheat the oven to 350 F. Generously grease 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.
Makes 6 to 8 servings.