Peel the bananas and slice them on a slight diagonal into slices about ½-inch thick. Set aside.
In a medium bowl, whisk together the flour, baking powder, cinnamon, and salt.
In a separate large bowl, whisk together the egg, milk, maple syrup, oil, vanilla extract, and melted, slightly cooled butter until well combined
Add the dry ingredients to the wet ingredients and mix until just combined. Do not overmix. Let the waffle batter rest for 5 minutes as you preheat the waffle maker.
After 5 minutes, give the batter a very gentle stir and dip each banana slice into the batter, making sure it is fully coated on both sides. Lift the slice and allow any excess batter to drip off for a few seconds.
Place the coated banana slices onto the preheated waffle maker, leaving a little space between each one if placing more than one slice at a time. Close the waffle maker, press down gently, and cook for about 4 minutes, or until the waffle bites are golden and cooked through. Repeat with the remaining banana slices.
For optional cinnamon sugar coating: Mix together the granulated sugar and cinnamon in a shallow bowl. As soon as the banana waffle bites come out of the waffle maker, toss or sprinkle them with the cinnamon sugar while they are still hot so that the coating sticks. If needed, brush a very small amount of melted butter on the waffles to help the coating stick.