Preheat your oven to 350°F (175°C). Gather your ingredients while the oven warms up.

In a mixing bowl, combine ground beef, onion, breadcrumbs, egg, milk, salt, and pepper. Mix thoroughly and press firmly into greased baking dish.

Bake the meatloaf for about 20 minutes until set and slightly browned.

While the meatloaf bakes, boil salted water and cook the macaroni according to package instructions until al dente. Drain and set aside.

In a saucepan, melt butter over medium heat. Whisk in flour to create a roux, then gradually add milk until thickened.

Stir in paprika, dry mustard, and the cheese until melted and creamy.

Toss the macaroni in the cheese sauce until well-coated, then pour over the partially baked meatloaf.

Sprinkle any remaining cheese on top and bake for an additional 25 minutes until bubbly and golden.

Let rest for a few minutes before serving.