Mary Berry's Apple and Lemon Sponge Cake • 225g unsalted butter, softened • 225g caster sugar • 4 large eggs • 225g self-raising flour • 1 tsp baking powder • Grated zest of 1 lemon • Juice of 1 lemon • 300g cooking apples, peeled and diced • Icing sugar, for dusting 1. Preheat the oven to 180°C (160°C fan) and grease and line a 23cm round cake tin. 2. In a bowl, cream together the butter and sugar until light and fluffy. 3. Beat in the eggs one at a time, then fold in the flour, baking powder,