Preheat your oven to 350°F (175°C).
Cook spaghetti according to package instructions until al dente; drain and set aside.
In a large skillet, sauté chopped onion and minced garlic until softened.
Add ground beef (or turkey) to the skillet, cooking until browned; drain excess fat.
Stir in marinara sauce and Italian seasoning; let simmer for 5 minutes.
In a large bowl, mix cooked spaghetti, ricotta cheese, and half of the mozzarella cheese.
Add the meat sauce to the spaghetti mixture and stir to combine.
Transfer the spaghetti mixture to a baking dish and top with remaining mozzarella and Parmesan cheese.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden.
Let cool for a few minutes before serving.