Open salmon and drain thoroughly. Place drained salmon in mixing bowl and flake evenly with a fork.Add onion, corn meal, flour, mayonnaise, and egg. Stir until well blended.Shape the mixture into patties about the size of an average burger or less.Cook in oil in skillet over medium heat until browned on each side. Turn once while frying.Note: The mayonnaise helps the patties hold their shape and keeps them from being too dry.