Preheat your oven to 375°F (190°C).

In a large mixing bowl, gently combine the ground beef, breadcrumbs, milk, egg, finely chopped onion, salt, and black pepper. Mix just until combined.

Transfer the meat mixture to a greased baking dish or a loaf pan and shape it into a loaf about 2 inches high.

In a separate bowl, whisk together the ketchup, brown sugar, and Worcestershire sauce until smooth. Set aside half for later.

Spread half of the glaze mixture evenly over the top of the shaped meatloaf.

Place the glazed meatloaf in the preheated oven and bake for 45 minutes.

After 45 minutes, remove the meatloaf from the oven and spread the remaining glaze over the top.

Return the meatloaf to the oven for another 15 minutes.

Check the internal temperature with a meat thermometer, aiming for 160°F (71°C).

Once it reaches the desired temperature, remove from the oven and let it rest for 10 minutes before slicing.