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.
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.
To Freeze: Freeze in oven ready container.
To Reheat: Bake in 350 degree oven for 30 minutes, triple cook time from frozen.