Spicy Baked Ziti

The basis for this recipe is from 2003 when I was involved with a summer program designed for life skills middle school students. My good friend (and now my boss!) spent our summers with these students participating in field trips, team building activities, arts and crafts and ...the most popular....cooking!  The following is the "spiced-up" version!

Ingredients:
1 pound dry ziti pasta
1 onion, chopped
1 pound hot Italian sausage
2 ( 26 ounce ) jars spaghetti sauce
6 ounces Provolone cheese, sliced
1 1/2 cups of sour cream
6 ounces mozzarella cheese, shredded
4 TBS. grated Parmesan cheese
Crushed red pepper flakes to taste ( depends on your definition 
of spicy!)

Preparation:
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 sausage over medium heat.  Add spaghetti sauce, and simmer 15 minutes.  Preheat the oven to 350 degrees F.  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.