Preheat the oven to 180C/350F/gas mark 4
Use a 450g/1 lb loaf tin.
Lightly grease the loaf tin. Sift the flour, nutmeg, sugar and baking powder into a bowl. Put the maple syrup and margarine in a saucepan with the water. Stir until the margarine has melted, then put aside to cool a little.
Mash the bananas and stir into the melted mixture. Pour into the flour and stir until evenly mixed. Pour into the loaf tin and bake for 1 hour 5 minutes. Turn out and cool on a wire rack.
Icing. Sift the icing sugar and add enough lemon juice to make a thick icing. Stir in the rind and pour over the cooled cake. Slice the remaining banana and arrange on the top. Serve in slices, spread with butter.
