Creating Hamburger Supreme Casserole is simple if you follow these straightforward steps:

1. Preheat the Oven: Start by preheating your oven to 350°F (175°C).
2. Brown the Beef: In a large skillet over medium heat, cook the ground beef until browned. Drain the excess fat.
3. Sauté Vegetables: Add the chopped onion and bell pepper to the skillet with the beef. Cook until softened, about 5 minutes.
4. Mix Ingredients: In a large mixing bowl, combine the cooked beef and vegetable mixture with the cooked pasta, diced tomatoes, sour cream, garlic powder, salt, pepper, and Italian seasoning. Mix until everything is well combined.
5. Transfer to Casserole Dish: Pour the mixture into a greased 9×13-inch casserole dish.
6. Add Cheese: Sprinkle the cheddar and mozzarella cheese evenly over the top of the casserole.
7. Bake: Place the casserole in the preheated oven and bake for 30-40 minutes, or until the cheese is melted and bubbly.
8. Cool: Remove from the oven and let cool for about 10 minutes before serving.

These steps will help you prepare a savory Hamburger Supreme Casserole that everyone will love!