2. Cook the spaghetti according to package instructions until al dente. Drain and set aside.
3. In a large pot, heat the olive oil over medium heat. Add the chopped onion and minced garlic, and sauté until the onion is translucent.
4. Add the marinara sauce, dried basil, dried oregano, salt, and black pepper to the pot. Stir to combine and let it simmer for 10 minutes.
5. In a mixing bowl, combine the ricotta cheese, 1 cup of mozzarella cheese, and 1/2 cup of Parmesan cheese.
6. In a baking dish, spread a thin layer of the marinara sauce mixture. Add half of the cooked spaghetti, then spread the ricotta cheese mixture on top. Add the remaining spaghetti and cover with the rest of the marinara sauce.
7. Sprinkle the remaining mozzarella and Parmesan cheese on top.
8. Bake in the preheated oven for 25-30 minutes, or until the cheese is melted and bubbly.
9. Let it cool for a few minutes before serving. Enjoy!
Notes:
This casserole can be made ahead of time and refrigerated. Just bake it when you're ready to eat.