Creating the perfect Cheeseburger Casserole is simple when you follow these steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C).
2. Cook the Beef: In a large skillet, brown the ground beef over medium heat. Drain any excess fat.
3. Add Vegetables: Stir in the diced onion and cook until softened, about 3-4 minutes.
4. Mix in Noodles: Add the uncooked egg noodles to the skillet, followed by the diced tomatoes, milk, and mustard. Stir well to combine.
5. Season: Season with salt and pepper to taste. Ensure everything is evenly mixed.
6. Transfer to Baking Dish: Pour the mixture into a greased 9×13-inch baking dish.
7. Top with Cheese: Sprinkle the shredded cheddar cheese evenly over the top.
8. Bake: Place the casserole in the oven and bake for 25-30 minutes, or until the noodles are tender and the cheese is bubbly and golden.
9. Let It Rest: Once baked, remove from the oven and let it sit for 5-10 minutes before serving.

By following these steps, you’ll have an incredible Cheeseburger Casserole that’s sure to impress.