Put the water and sugar in a pot on the stove to come to a boil - do not stir under any circumstances.
Once it gains a nice caramel-brown color remove it from the stove and add the butter, stir until it melts. Pour the caramel into a buttered cake form.
Pour the mixture over the apples and bake the cake at 356°F (180 °C) for 30 min. or till your toothpick comes out dry. Invert the ready cake into a suitable plate.