Step 1

Preheat the oven to 350 degrees F.

Step 2

Lightly grease a 9x5-inch loaf pan.

Step 3

In a large bowl, combine the ground beef, the egg, the onion, the milk, and the breadcrumbs.

Step 4

Season the beef mixture with salt and pepper and mix to combine.

Step 5

Transfer the beef mixture to the prepared loaf pan.

Step 6

In a small bowl, mix the ketchup, the brown sugar, and the mustard together until well combined.

Step 7

Pour the sauce over the meatloaf and evenly spread it over the top.

Step 8

Bake the meatloaf until it is no longer pink in the center and reaches an internal temperature of 160 degrees F, about 1 hour.

Step 9

Serve.