Pre-heat oven to 450 degrees F.
Prepare macaroni and cheese as indicated on box. Set aside.
In a skillet, add ground beef and onion, season with salt and pepper. Brown meat and drain grease. Mix beef, onions, macaroni and cheese, and Italian seasoning in a shallow baking dish. Top with shredded mozzarella and cheddar. Bake until cheese is melted.