Baked Ziti

Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish with cooking spray or olive oil.
Bring a large pot of salted water to a boil and cook the ziti according to package directions until al dente, then drain the pasta and return it to the warm pot.
While the pasta cooks, heat 1 tablespoon of olive oil in a large skillet over medium-high heat, then add the Italian sausage and onion, breaking up the meat with a spoon, and cook for 7-8 minutes until the sausage is browned and the onion is soft; stir in the minced garlic and cook for 1 more minute until fragrant.
In a medium bowl, combine the ricotta cheese, egg, parsley, salt, pepper, 1 cup of the shredded mozzarella, and 1/2 cup of the Parmesan cheese, stirring until the mixture is smooth and fully incorporated.
Add the cooked sausage mixture, marinara sauce, and ricotta cheese mixture to the pot with the drained pasta, then gently fold everything together until the pasta is evenly coated.
Transfer the pasta mixture to the prepared baking dish and spread it into an even layer, then top with the remaining 1 cup of mozzarella and 1/2 cup of Parmesan cheese.
Cover the dish tightly with foil and bake for 20 minutes, then remove the foil and continue baking for another 15-20 minutes until the cheese is completely melted and the edges are bubbling.
Let the baked ziti rest for 10 minutes before serving to allow the sauce to set slightly for easier serving.