Preheat the oven to 350°F
Grease a loaf pan or line a baking sheet with parchment paper
In a large bowl, combine ground beef, breadcrumbs, egg, milk, chopped onion, garlic, salt, pepper, and ketchup
Mix gently until just combined
Shape the mixture into a loaf
Place the loaf in the prepared pan or on the baking sheet
Spread ketchup or meatloaf glaze over the top
Bake for 50 to 60 minutes
Check that the internal temperature reaches 160°F
Let the meatloaf rest for 10 minutes
Slice and serve