Start this recipe by placing the peach slices and raspberries in the bottom of an oven-proof dish. Sprinkle over the lemon zest and caster sugar and put aside. Meanwhile, make the sponge topping. Beat together the butter and sugar until pale and fluffy, then beat in the eggs, adding 1 tbsp flour with the second egg. Sift over the remaining flour and baking powder and fold in gently with the milk and vanilla essence. Spoon the sponge mixture roughly over the fruit in the oven dish and bake in the oven at 180`c for 45 minutes until golden brown and cooked through. You may need to cover the cake with foil after 30 minutes of cooking time if it is browning too quickly). When ready, remove from the oven and allow to rest for 5 minutes before dusting with icing sugar and serve whilst still hot.