In a large mixing bowl, place the beef, bread crumbs, scallions, onions, green peppers, garlic, eggs, black pepper, salt, meatloaf seasoning, beef gravy, and Cheddar. Using a wooden spoon, mix the ingredients until they are evenly distributed.
Turn the meat mixture out into a large roasting pan. Form into a loaf shape. Cover the pan with aluminum foil, and bake for 1 1/2 hours.
Remove the roasting pan with the loaf from the oven, quickly closing the door to keep the oven hot. Remove the aluminum foil. Spread the top and sides of the loaf with the tomato paste. Roast, uncovered, for another 15 to 20 minutes, or until an inserted meat thermometer reaches 155 degrees F.
Let meatloaf rest for 10 minutes before slicing and serving.