Preheat the oven to 375°F (190°C).

Cook the spaghetti according to package instructions until al dente. Drain and set aside.

In a large skillet, cook the ground beef with the chopped onion and minced garlic over medium heat until the meat is browned. Drain excess fat.

Stir in the marinara sauce, adding salt and pepper to taste. Let it simmer for 5 minutes.

In a large mixing bowl, combine the drained spaghetti, ricotta cheese, and half of the mozzarella cheese, mixing well.

Spread half of the beef mixture on the bottom of a baking dish, then add the spaghetti mixture on top, followed by the remaining beef mixture.

Sprinkle the rest of the mozzarella and the grated Parmesan cheese evenly over the top.

Bake in the preheated oven for about 25-30 minutes or until the cheese is bubbly and golden brown.

Let it rest for a few minutes before serving. Enjoy with a sprinkle of fresh basil on top!