Preheat the oven to 350°F. Line a rimmed baking pan with aluminum foil and spray with cooking spray.
In a small pan, cook onions in butter over medium low heat until tender. Let them cool completely.
½ medium onion, 1 teaspoon butter
In a medium bowl, combine eggs, milk, and breadcrumbs. Let the mixture sit for 5-10 minutes.
2 large eggs, ¾ cup seasoned bread crumbs, ½ cup milk
Add the ground beef, cooked onions, soaked breadcrumbs, 2 tablespoons of ketchup, garlic powder, parsley, and salt & pepper to the bowl. Mix until just combined.
2 pounds lean ground beef, 2 tablespoon ketchup, 1 teaspoon garlic powder, 2 teaspoons dried parsley, 1 teaspoon kosher salt, 1 teaspoon black pepper
Form into an 8"x4" loaf on the prepared baking pan and bake for 40 minutes.
While the meatloaf is cooking, combine the BBQ sauce and ketchup and brown sugar to make Meatloaf Sauce. Spread mixture over the meatloaf and bake for an additional 15-30 minutes or until cooked through and the meatloaf reaches an internal temperature of 160°F. Broil for 1-2 minutes if desired.
½ cup barbecue sauce, ½ cup ketchup, 2 tablespoons brown sugar
Let the meatloaf rest for 10 minutes before slicing and serving.