Preheat the oven to 350°F (175°C) and prepare a half sheet pan lined with aluminum foil.

In a medium skillet, heat olive oil over medium heat, add diced onions, and sauté for about 10 minutes until browned.

In the mixing bowl, combine sautéed onions, ground beef, breadcrumbs, beaten eggs, whole milk, salt, black pepper, onion powder, garlic powder, Italian seasoning, half of the ketchup, Worcestershire sauce, and parsley. Mix gently.

Shape the mixture into a loaf and place it on the prepared pan, about 2 inches high.

In a small bowl, whisk together remaining ketchup and brown sugar, then spread over the meatloaf.

Cover with foil and bake for about 45 minutes to 1 hour or until internal temperature reaches 160°F (70°C).

Remove from oven, let rest for 10-15 minutes, then slice and serve with fresh parsley.