Heat the oven to 350 degrees F. Thoroughly mix the beef, 1/2 cup soup, the onion, bread crumbs, egg, salt and black pepper in a large bowl. Place the beef mixture into a 13x9x2-inch baking pan and firmly shape into an 8x4-inch loaf.
Bake for 1 hour 10 minutes or until the meatloaf is cooked through. Let the meatloaf stand for 10 minutes before slicing.
Heat 2 tablespoons pan drippings, the remaining soup and the water in a 1-quart saucepan over medium heat until the mixture is hot and bubbling, stirring occasionally. Serve with the meatloaf.