Heat the olive oil in a large, heavy pot or large, deep skillet over medium heat. When the oil is hot, but not smoking, add the onions. Cook for 3 minutes, stirring frequently.

Add the garlic; cook 1 minute, stirring frequently.

Add the sausage to the pot; raise the heat to medium-high. Cook for 5-6 minutes until the meat is browned, stirring frequently and breaking any large pieces with a wooden spoon or a spatula.

Add the tomatoes and pasta sauce the pot, stir well.

Bring the sauce to a simmer, lower heat to medium-low and cover. Cook the sauce for 40-45 minutes, stirring occasionally. Keep the sauce at a simmer. Lower the heat if it’s boiling too vigorously.

Preheat oven to 350°F

While the sauce cooks, start the pasta.

Bring a large pot of water to a full boil. Add 1 tablespoon salt and the pasta. Cook the ziti to package directions for al-dente.

Drain the pasta well and set aside. (If desired, reserve about a cup of the pasta cooking water to loosen the sauce if needed.)

Combine the ziti and the sauce in the larger of the two pots. Stir gently.

Use a large, oven proof casserole dish or baking pan (9x13).

Spoon about half of the ziti pasta mixture into the casserole dish.

Sprinkle the top with half the mozzarella cheese and half the parmesan cheese.

Add the remaining pasta and top with the remaining mozzarella and parmesan cheese.

Place the casserole dish on a rimmed baking sheet, just in case it bubbles over. Bake the pasta for 15-20 minutes until the cheese is melted.

Garnish with a little chopped parsley and serve with extra parmesan cheese and crushed red pepper, if desired.