Heat a large skillet over medium-high heat and add the ground beef. Cook for 5-7 minutes, breaking it up with a spatula, until it is browned and no longer pink. Drain any excess fat.

Add the diced onion and minced garlic to the skillet with the browned beef. Sauté for 2-3 minutes until the onion becomes translucent and fragrant.

Stir in the tomato sauce, diced tomatoes, Italian seasoning, salt, and black pepper into the beef mixture. Let it simmer for about 5 minutes.

In a separate pot, bring salted water to a boil, then add the elbow macaroni. Cook for 8-10 minutes until al dente. Drain and set aside.

In a large mixing bowl, combine the cooked macaroni with the beef mixture, cheddar cheese, mozzarella cheese, and sour cream. Stir until fully incorporated.

Transfer the mixture into a greased baking dish, top with Parmesan cheese. Preheat oven to 375°F (190°C) and bake for 25-30 minutes.

Remove from the oven and let it cool for 5 minutes before serving.