Pre-heat the oven to 180ºC/350ºF/Gas Mark 4. Grease and line a 20cm (8 inch) deep tin.
Mix together the apples and sultanas then pour over the milk and set to one side.
Place the soft brown sugar, flour, Baking Powder, spice and lemon rind in a bowl. Gradually beat in the butter and egg.
Finally beat in the apple and sultana mixture. Spoon the mixture into the tin, sprinkle the demerara sugar over the top and bake for approximately 1 hour 10 minutes until well risen and firm to the touch.
Cool slightly before turning out onto a wire rack.