Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan.

In a large mixing bowl, combine the ground beef, onion, milk, eggs, breadcrumbs, Worcestershire sauce, garlic powder, salt, and pepper. Mix gently until just combined.

Transfer the meat mixture to the prepared loaf pan and shape it into a loaf.

In a separate bowl, whisk together ketchup, brown sugar, and Dijon mustard. Spread half of the mixture over the top of the meatloaf.

Bake the meatloaf uncovered for 45 minutes.

After 45 minutes, brush the remaining glaze over the top and bake for an additional 15-20 minutes or until the internal temperature reaches 160°F (71°C).

Let the meatloaf rest for about 10 minutes before slicing.