Preheat the oven to 350 degrees and lightly grease a loaf pan.
In a large bowl combine the ground beef, breadcrumbs, egg, onion, 2 tablespoons of the ketchup, salt, pepper, and garlic powder. Mix just until the ingredients are evenly distributed.
Press the mixture into the prepared loaf pan and smooth the top.
In a small bowl stir together the remaining 2 tablespoons ketchup, brown sugar, and vinegar until smooth.
Spread the glaze evenly over the meatloaf.
Bake for 55 to 60 minutes until the internal temperature reaches 160 degrees. Let the meatloaf rest for 10 minutes before slicing.