In a large mixing bowl, combine the egg, bread crumbs, onion, salt and pepper.
Add the ground beef to the mixture and mix well. Press half of the beef mixture into the bottom of a greased loaf pan. Sprinkle 3/4 cup of the pepper jack cheese over meat to within 1/2 inch of sides. Press remaining beef mixture over cheese.
Bake uncovered for 50-55 minutes or until the meat is no longer pink. Sprinkle the remaining cheese over meatloaf and bake an additional 5 minutes until cheese is melted.
Let meatloaf stand for 10 minutes before slicing. Serve with salsa if desired.