Preheat your oven to 375°F (190°C).

In a large skillet, heat olive oil over medium heat. Add the Italian sausage, breaking it apart with a spoon. Cook for about 5-7 minutes until browned and cooked through.

While the sausage is cooking, bring a large pot of salted water to a boil. Add the ziti pasta and cook according to package instructions until al dente, about 8-10 minutes. Drain and set aside.

In a separate bowl, combine ricotta cheese with a pinch of salt and pepper. Optionally, mix in some shredded mozzarella cheese.

In the skillet with the cooked sausage, add the chopped onion and minced garlic. Sauté for about 3-4 minutes until the onion is translucent. Stir in the crushed tomatoes, oregano, and basil. Let the sauce simmer for about 10 minutes.

In a large mixing bowl, combine the cooked ziti with the sausage sauce. Gently fold in the ricotta cheese mixture and half of the shredded mozzarella cheese. Transfer this mixture into a greased 9x13-inch baking dish.

Sprinkle the remaining mozzarella cheese and grated Parmesan cheese evenly over the top. Bake for 25-30 minutes until the cheese is bubbly and golden brown.

Let the baked ziti cool for a few minutes before serving. Garnish with fresh basil if desired.