Preheat the oven to 350 degrees. In a large bowl, combine the ground beef, crushed Ritz crackers, milk, egg, onion, green bell pepper, salt, and black pepper. Mix until the ingredients are evenly distributed.
Shape the mixture into a loaf and place it in a loaf pan. Bake for 60 minutes, or until the internal temperature reaches 160 degrees.
While the meatloaf bakes, melt the butter in a skillet over medium heat. Stir in the flour and cook for one minute to form a roux.
Slowly whisk in the beef broth. Continue stirring until the gravy thickens, about 3 to 4 minutes. Season with a pinch of salt and pepper if needed.
Remove the meatloaf from the oven and let it rest for 5 minutes. Slice and serve with the brown gravy spooned over the top.