Preheat your oven to 350°F (175°C). Then, lightly grease a loaf pan or line a baking sheet with a greased wire rack.

In a large mixing bowl, beat the egg and then whisk in the milk and Worcestershire sauce.

Add the breadcrumbs, chopped onion, green bell pepper, garlic powder, parsley, salt, and pepper to the wet ingredients and stir gently to combine.

Add the ground beef to the mixture and gently mix with your hands until all ingredients are evenly distributed, avoiding overmixing to prevent a tough meatloaf.

Transfer the meat mixture to the prepared loaf pan or form into a loaf shape on the wire rack and bake for 45 minutes.

While baking, whisk together ketchup, brown sugar, apple cider vinegar, and mustard in a small bowl to make the glaze.

After 45 minutes, remove the meatloaf from the oven, spread the glaze over the top, and return to the oven for another 15-20 minutes, or until the internal temperature reaches 160°F (71°C).