Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 4 ingredients in a bowl. Combine egg, buttermilk, and butter; add to dry ingredients, stirring until smooth. Stir in banana.
Spoon 1/4 cup batter for each pancake onto a hot griddle or skillet coated with cooking spray. Turn pancakes when tops are bubbly and edges look cooked. Serve with syrup.