In a small bowl, whisk the flour with the baking powder, baking soda and salt. In a medium bowl, beat the eggs with the buttermilk. Quickly stir in the flour mixture, then stir in the melted butter and blueberries.
Heat a griddle or a large nonstick skillet over moderately low heat and spray with nonstick cooking spray. Ladle 1/4 cup of the batter per pancake onto the griddle, leaving room for the pancakes to spread. Gently lay one banana slice in the center of each pancake and cook until bubbles appear on the surface, 3 to 4 minutes. Flip the pancakes and cook until golden brown on the second side, 2 to 3 minutes longer. Generously dust the blueberry-banana pancakes with confectioners' sugar and serve with maple syrup.