Preheat the oven to 350°F (175°C) and lightly grease a 9×13-inch baking dish with nonstick spray.

Bring about 2 quarts of water to a boil in a large pot. Add 1 tablespoon salt, then cook the pasta until al dente. Drain and set aside.

While the pasta cooks, heat olive oil in a large skillet over medium heat. Add diced onion and cook until translucent.

Add the minced garlic and cook for about 1 minute until fragrant.

Add the beef sausage, breaking it apart as it cooks. Cook until browned. Drain excess fat if needed.

Stir in marinara sauce and Italian seasoning. Season with salt and pepper to taste.

Add the cooked pasta and mix well so it’s fully coated with the sauce.

Spread half of the pasta mixture into the prepared baking dish.

Smooth the ricotta cheese, then drop spoonfuls evenly over the pasta. Sprinkle parmesan and half of the mozzarella cheese.

Add the remaining pasta mixture on top.

Finish with the rest of the mozzarella cheese.

Cover with foil and bake for 20–25 minutes until the cheese is melted and bubbly.

Let the Cheesy Baked Ziti rest for 5 minutes before serving.