Preheat oven to 350 degrees Fahrenheit.
Place the bananas, eggs, tahini, and cinnamon (if using) in a blender. Blend until smooth.
In a large mixing bowl, stir together the oats and the baking powder.
Pour the contents of the blender into the bowl and stir to combine.
Grease a 9x12 pan.
Spread the contents of the bowl into the greased pan.
Bake for 25-30 minutes or until a knife inserted into the centre comes out clean.
Allow to cool fully before cutting into 24 finger-sized pieces.