Place sugar, butter and egg yolk in a mixing bowl and then cream well, then add the flour, baking powder, vanilla extract and water. Beat to mix and pour into well-greased and floured oblong baking pans. Now spread the top of the cake with three bananas sliced very thin. Place in a moderate oven and bake for thirty-five minutes. Use the white of egg and half glass of apple jelly for a meringue.