Preheat the oven to 375°F (190°C). Lightly grease a loaf pan or line a baking sheet with parchment paper.
In a large bowl, combine the ground beef, breadcrumbs, milk, egg, diced onion, minced garlic, ketchup, Worcestershire sauce, Italian seasoning, salt, black pepper, and onion powder.
Gently mix until the ingredients are just combined. Do not overmix.
Shape the mixture into a loaf approximately 9 × 5 inches and place it on the prepared baking sheet or in the loaf pan.
In a small bowl, whisk together the ketchup, brown sugar, apple cider vinegar, Worcestershire sauce, and garlic powder.
Spread about half of the glaze over the top of the meatloaf.
Bake for 45 minutes.
Remove from the oven and spread the remaining glaze over the top.
Return to the oven and bake for another 15–20 minutes, or until the center reaches 160°F (71°C).
Remove from the oven and let the meatloaf rest for 10–15 minutes before slicing.
Slice and serve warm with mashed potatoes, roasted vegetables, green beans, or your favorite sides.