Cook the elbow macaroni according to the package instructions in a large pot of boiling salted water. Drain and set aside.
In a skillet over medium heat, add the ground beef, diced onion, and minced garlic. Cook until the beef is browned and the onion is tender, about 5-7 minutes. Drain any excess fat.
Stir in the tomato sauce, diced tomatoes (with their juice), Italian seasoning, salt, and black pepper. Simmer the mixture for about 5 minutes.
Add the drained macaroni to the skillet, stirring until well combined with the beef mixture.
Remove the skillet from heat and stir in the milk and half of the cheddar and mozzarella cheese, mixing until everything is evenly distributed.
If you prefer a baked version, preheat your oven to 350°F (175°C). Transfer the mixture into a 9x13 inch baking dish, top with the remaining cheddar and mozzarella cheese, and bake for 15-20 minutes until the cheese is melted and bubbly.
If not baking, simply serve the cheesy ground beef pasta directly from the skillet.