01 -
Preheat the oven to 350°F (175°C).
02 -
In a mixing bowl, combine ground beef, diced onion, breadcrumbs, egg, milk, salt, and pepper. Mix well and press into the bottom of a greased baking dish.
03 -
Bake the meatloaf for about 20 minutes.
04 -
Cook macaroni according to package directions until al dente; drain.
05 -
In a saucepan over medium heat, melt butter. Stir in flour for one minute before gradually whisking in milk until thickened. Add salt, pepper, paprika, and dry mustard, then stir in shredded cheddar cheese until melted.
06 -
Combine cooked macaroni with cheese sauce and mix thoroughly.
07 -
Pour the macaroni and cheese mixture over the baked meatloaf layer in the dish. Sprinkle any remaining cheese on top.
08 -
Bake the assembled casserole for an additional 25 minutes until the cheese is melted and bubbly.