Preheat your oven to 350°F (175°C) and lightly grease a 9x13-inch baking dish.

In a large mixing bowl, combine the ground beef, breadcrumbs, egg, milk, finely chopped onion, garlic powder, and barbecue sauce. Mix until combined.

Transfer the meat mixture into the greased baking dish and press it evenly into the bottom. Bake for 25-30 minutes or until browned and internal temperature is at least 160°F (71°C).

While the meatloaf is baking, cook the elbow macaroni according to package instructions until al dente, around 7-8 minutes. Drain and set aside.

In a medium saucepan over medium heat, melt 2 tablespoons of butter, then whisk in 2 tablespoons of flour. Add 2 cups of milk slowly while stirring until thickened.

Remove from heat and stir in 2 cups of shredded cheddar cheese and 1 teaspoon of paprika. Mix until the cheese melts.

In a large bowl, gently fold the cooked elbow macaroni into the cheese sauce until well-coated.

Spread the mac and cheese mixture over the cooked meatloaf. Bake for an additional 20-25 minutes until bubbly and golden brown.

Let it cool for a few minutes before slicing and serving. Enjoy with a simple side salad or steamed vegetables.