Slice the apples, which have been cored and pared. Then peel and slice the bananas. Place fruit in alternate layers in a greased baking dish, sprinkling each layer with 1/3 cup of sugar and 3 Tbsp butter. Pour the boiling water over the fruit; cover the dish closely and bake for 1/2 hour. Remove the cover and continue the baking for 10 minutes longer. Serve with the juice that forms in the baking pan (could be done in Dutch oven).