Preheat the oven to 350°F.
In a small bowl, whisk together the egg, milk, ketchup, and Worcestershire sauce until smooth and well combined.
In a separate bowl, mix the breadcrumbs, Italian seasoning, garlic powder, salt, and black pepper so the seasonings are evenly distributed.
Add the ground beef, minced onion, egg mixture, and breadcrumb mixture to a large bowl. Gently mix with your hands until just combined, being careful not to overmix.
Shape the mixture into a loaf about 8 inches long and 4 inches wide, then place it on your prepared baking sheet or dish.
If using the glaze, stir together the ketchup, brown sugar, Worcestershire sauce, and mustard. Spread evenly over the top of the meatloaf. For a simpler version, spread plain ketchup over the top.
Bake for 50 to 55 minutes, or until the internal temperature reaches 165°F.
Let the meatloaf rest for 5 to 10 minutes before slicing and serving.