Preheat oven to 375. Boil pasta in salted water according to Al dente instructions, drain. Meanwhile, set a large Dutch oven or stockpot over medium-high heat. Add the sausage, onion and garlic and cook, breaking up the meat with a spoon, until the meat is browned and the onions are softened, about 8 minutes. Drain off any excess fat into a small bowl, discard.

Add the marinara sauce, tomato sauce, salt and seasonings and heavy cream, stir until combined. Stir in the cooked ziti and 1½ cups shredded mozzarella. Place pasta mixture into 9x13 casserole pan.

Top with the fresh mozzarella slices and remaining ½ cup shredded mozzarella, cover the baking dish with foil and bake for 20 minutes, until the pasta is tender. Remove the dish from the oven, discard the foil and sprinkle with the Parmesan. Return to the oven uncovered and bake for about 5 more minutes, until the cheese is melted and the sauce is bubbling.