I start by heating olive oil over medium heat, then cook the diced onion for about three minutes. Once the onion softens, I add the minced garlic and cook just a minute until fragrant.
Then I add the sausage (casings removed, pieces broken up) and crank the heat to medium-high, cooking it for 5-6 minutes until browned and well broken up.
Once the meat is browned, I stir in the diced tomatoes and the jarred pasta sauce. I bring everything to a gentle simmer, then lower the heat to medium-low and cover. I let it cook for about 40-45 minutes, stirring occasionally.
If it boils too hard, I lower the heat — this slow simmer helps the flavors meld and the sauce thicken nicely.
While the sauce is simmering, I preheat the oven to 350°F (about 175°C) and cook the ziti according to package directions just to al dente, then drain it well. I combine the pasta and sauce in a large pot or bowl.
Then layer half of that in my casserole dish, sprinkle half of the mozzarella and Parmesan, add the rest of the pasta mixture, and top with the remaining cheeses.
I bake it for 15-20 minutes until the cheese is melted and bubbly. Then I garnish with chopped parsley, extra Parmesan, and a bit of crushed red pepper if I’m feeling spicy.