In stand mixer on low with the paddle attachment, mash the bananas until soft. The bananas should be very well broken down. Add the melted butter, sugar, egg, and rum.
In a separate bowl combing the dry ingredients: flour, baking soda, and salt. Mix thoroughly.
With the mixer still on low, add the dry ingredients. Mix until clear. Pour the batter in a greased 8 inch loaf pan.
In a small bowl combine the sanding sugar and a few drops of rum. Mix until moistened. Sprinkled the flavoured sugar over the top of the batter. Bake for 50 minutes. Check for doneness with a toothpick or until a inserted knife comes out clean.
Let the loaf cool on a rack in the pan for at least 10 minutes. Remove from the pan and let cool completely. Serves 8-10 slices.