Preheat the oven to 350 degrees.
Cook the ziti according to package directions until nearly al dente'.
Drain and set cooked pasta aside.
Mince the onion.
Heat a frying pan or large skillet over medium heat and brown the sausage with the minced onion and garlic.
Drain the excess grease from the cooked sausage and discard it.
Stir the Italian seasoning into the sausage.
Spray a deep 3.5-quart casserole dish with non-stick cooking spray.
Dump ½ of the cooked ziti in the bottom of the dish.
Pour one can of sauce over the ziti.
Sprinkle on ½ of the sausage.
Layer the provolone cheese in an even layer over the sausage.
Spread the sour cream over the top of the provolone the best you can.
Add the rest of the pasta.
Pour a second can of pasta sauce over the ziti.
Sprinkle the rest of the sausage then sprinkle with mozzarella cheese or Italian Cheese.
Cover the ziti dish with aluminum foil and bake for 20 minutes at 350 degrees. Then, remove the foil and bake for an additional 10 minutes.
The cheese should be melted and golden brown.
Cool slightly before serving, and garnish with fresh parsley if desired.
Store leftover baked ziti covered with plastic wrap or with the lid of the casserole dish.