Preheat your oven to 350°F (175°C) and grease a loaf pan or line it with parchment paper.

In a large mixing bowl, combine the lean ground beef, breadcrumbs, chopped onion, milk, beaten egg, Worcestershire sauce, parsley, salt, garlic powder, and pepper. Mix well for 2-3 minutes.

Transfer the meat mixture into the prepared loaf pan and mold it into a smooth, even shape.

In a small bowl, mix together ketchup, brown sugar, and apple cider vinegar or lemon juice to create the glaze. Spread evenly over the molded meatloaf.

Place the glazed meatloaf in the oven and bake uncovered for about 55 minutes until the internal temperature reaches 160°F (71°C).

Allow the meatloaf to rest for 8-10 minutes before slicing to maintain juiciness.