I got this recipe from csaceliacs.org, which is a great source for celiacs. I used my favorite gluten free flour mix (Recipe #149852), which contains xanthan gum. I think the gum really contributed to the great texture.
Beat in the eggs, vanilla and bananas, beat until fairly smooth.
In another bowl mix together the flour and baking powder.
Beat the dry ingredients into the wet ingredients until well combined (I had to switch from an electric mixer to a spoon near the end of the mixing as the batter got too stiff for my poor little mixer).
Stir in the nuts, if desired.
Put the batter in a greased 5x9 loaf pan and spread evenly.
Bake at 325 degrees for one hour and 20 minutes, or until a toothpick inserted in the center comes out clean.