Preheat your oven to 350°F (175°C) and grease a loaf pan.

In a large mixing bowl, combine the lean ground beef, breadcrumbs, onion, milk, egg, Worcestershire sauce, parsley, garlic powder, salt, and pepper.

Transfer the meat mixture into the prepared loaf pan, shaping it evenly.

In a small bowl, whisk together ketchup, brown sugar, and apple cider vinegar until smooth, then spread over the meatloaf.

Place the loaf pan in the oven and bake uncovered for about 55 minutes.

Let the meatloaf rest for 8–10 minutes before slicing.