Preheat the oven to 350ºF. In a small bowl whisk together the egg, milk, and Worcestershire sauce. In a separate small bowl, stir together the breadcrumbs, Italian seasoning, garlic powder, salt, and pepper. Mince the onion.
Add the ground beef, egg mixture, breadcrumb mixture, and minced onion to a large bowl. Use your hands to mix the ingredients together until evenly combined. Avoid over mixing.
Place the meat mixture on a rimmed baking dish and shape it into a loaf that is approximately 4-inches wide, 8-inches long, and 2-inches tall.
In a separate small bowl, stir together the glaze ingredients (ketchup, brown sugar, Worcestershire sauce, and mustard). Spread the glaze evenly over the top and sides of the meatloaf.
Bake the meatloaf for 50-55 minutes, or until the internal temperature reaches 165ºF. Allow it to rest for 5-10 minutes after baking, then slice and serve.
*Ground beef is the base for this recipe, and I suggest using 80/20 (20% fat) ground beef. This is really important as it not only gives flavor, but it also stops the loaf from drying out.**The sugar in the meatloaf sauce adds sweetness and the most delicious caramelization once baked. But I know ketchup is already pretty sweet, so feel free to use half the amount of sugar to suit your tastes.