Preheat the oven to 180°C (160 °fan/ Gas 4/ 350°F) and lightly grease a 2 litre baking dish.
Cream together the softened butter and sugar until pale and fluffy.
125 g Butter, 125 g Golden Caster Sugar
Beat in the eggs and vanilla extract.
2 Eggs, 1 teaspoon Vanilla Extract
Fold in the flour.
125 g Self Raising Flour
Peel, core, and thinly slice the apples and lay them on the bottom of a buttered 2 litre baking dish.
2 Cooking Apples
Top the apples with the sponge mixture and use the back of a spoon to spread it out evenly.
Whisk together the dark brown sugar and boiling water in a jug until the sugar has dissolved. Pour this on top of the sponge.
140 g Dark Brown Sugar, 250 ml Boiling Water
Bake in the oven for 40-45 minutes until golden brown.