Preheat your oven to 350°F (175°C). Line a baking sheet with aluminum foil for easy cleanup.
In a large mixing bowl, combine the ground beef, diced onion, bread crumbs, and milk. Add the eggs, tomato paste, garlic powder, onion powder, salt, and pepper. Mix gently until well combined.
Shape the meat mixture into a loaf and place it on the prepared baking sheet or pack it into a greased loaf pan.
Bake uncovered for about 40 minutes. Meanwhile, mix together the ketchup and white vinegar in a small bowl.
After 40 minutes, spread the ketchup mixture over the meatloaf and return it to the oven for another 10 minutes or until fully cooked.
Let the meatloaf rest for about 10 minutes before slicing and serving.
Slice and serve warm with your favorite sides.