Preheat oven to 350°F degrees.
Mix ground beef in large bowl.
Add breadcrumbs, eggs, and diced onion.
Pour milk over meat mixture gently.
Season with salt, pepper, garlic powder.
Mix ingredients until just combined together.
Shape mixture into loaf pan carefully.
Combine brown sugar, ketchup, vinegar separately.
Spread glaze over meatloaf top evenly.
Bake for 60 minutes until done.
Check internal temperature reaches 160°F degrees.
Rest meatloaf for 10 minutes before.
Slice and serve while still warm.