Preheat oven to 350 degrees F. Lightly grease a 4"x 8" loaf pan. (If using dextrose, decrease temp to 300 degrees F.)
In a large bowl, mash the bananas with a fork. Add the eggs, melted butter and vanilla extract. Stir until smooth.
In a medium bowl, stir together the sugar (or dextrose), rice flour, potato starch, tapioca starch, cinnamon, baking powder, soda and salt.
Add the flour mixture to the banana mixture and blend well.
Pour batter into prepared loaf pan and bake for 35 to 40 minutes, or until a toothpick inserted near the center comes out clean. (If using dextrose, bake 60 to 65 minutes at 300.)
Cool completely on a wire rack. Remove from pan, slice and serve.