Step 1

Arrange a rack in the middle of the oven and heat the oven to 350°F.

Step 2

Bring a large pot of heavily salted water to a boil over high heat. Meanwhile, prepare the aromatics, cheese, and sausage.

Step 3

Dice 1/2 medium yellow onion (about 1/2 cup). Mince 4 garlic cloves. Cut 1 pound mozzarella cheese into 1/2-inch cubes (about 3 cups). Finely grate 2 ounces Parmesan cheese (about 1 packed cup), or measure out 2/3 cup store-bought grated. Remove the casings from 1 pound Italian sausage if needed.

Step 4

Heat 2 tablespoons olive oil in a large skillet over medium heat until shimmering. Add the onion and cook until softened, 3 to 4 minutes. Add the garlic and cook until fragrant, 30 seconds to 1 minute.

Step 5

Add the sausage, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper. Cook, breaking up the sausage with a wooden spoon or spatula into small pieces, until browned and cooked through, 6 to 8 minutes. Add 1 jar of the marinara sauce (about 3 cups) and stir to combine, scraping up any browned bits from the bottom of the pan. Remove the pan from the heat.

Step 6

Add 1 pound rigatoni pasta to the boiling water and cook according to package directions for 2 minutes less than al dente, about 8 minutes. Drain the pasta and return it to the now-empty pot off the heat.

Step 7

Add the sausage mixture and remaining 1 jar marinara sauce to the pasta and stir to combine. Add half of the mozzarella and fold it in.

Step 8

Transfer the mixture to a 9x13-inch baking dish, or divide between 2 (8-inch) baking dishes or disposable foil trays. (Use a metal or disposable baking dish if you’re planning to freeze this.) Sprinkle with the remaining mozzarella and Parmesan.

Step 9

Bake until the edges are bubbling and the cheese on top is completely melted and browned in spots, about 30 minutes. Let cool for 5 to 10 minutes before serving. Garnish with chopped fresh parsley leaves if using.