Preheat the oven to 180°C/gas mark 4
Butter an 18cm round cake tin.
Mix the ground mixed spice with the flour in a large bowl, then add all of the remaining ingredients except for the apples.
Beat together for 2–3 minutes until well mixed and add the 4 diced apples. Fold in carefully.
Spoon the cake mixture into the prepared tin and arrange the sliced apples over the top before sprinkling the demerara sugar mix evenly over the top of the cake and apples.
Bake in the oven for 45 – 50 minutes, or until a skewer inserted in the middle of the cake comes out clean.
Allow the cake to cool in the tin for a few minutes before turning out on to a wire rack.
Allow to cool completely before slicing and serving.