Preheat the oven to 180°C
Stew the apples: In a saucepan, place the peeled, cored, and sliced apples with the caster sugar and water. Cook gently over medium heat for 5-7 minutes until the apples soften but still hold their shape. Transfer the stewed apples to the base of a greased 8inch baking dish.
In a mixing bowl, sieve in the flour and add in the softened butter, sugar and crack in the eggs. Mix together until light and fluffy, using a hand mixer or electric whisk.
Spread the batter: Carefully spoon the sponge mixture over the stewed apples, spreading it evenly to cover the fruit.
Bake the pudding: Place the dish in the preheated oven and bake for 40-45 minutes, or until the sponge is golden and a skewer inserted into the center comes out
clean.
