Grease and line a 9 inch square baking tray.
Peel and core the apples. Finely chop two of the apples, place in a bowl. Cover and keep aside. Chop the other apple into half and slice each half into thin slices and keep aside. Coat with lemon juice if required, to prevent browning.
Preheat the oven at 180 degrees celsius.
Add the apple cider vinegar to 1 CUP milk and keep aside for 5 mins.
In a large bowl, sieve the flours, cinnamon, ginger, baking powder and keep aside.
In another large bowl, whisk well the coconut sugar, milk with apple cider vinegar, oil, vanilla extract, until well combined.
To the wet ingredients, add the dry ingredients, stir until combined. Do not over mix. Towards the end, add the finely chopped apples and mix to combine. Add 2 tbsp of milk if if you feel that the batter is too thick.
Scrape this cake batter into the prepared baking tin.
Place the sliced apples on top in a single layer, decorating in anyway you like.
Sprinkle with 2 tbsp granulated sugar and keep in a centered rack to bake in the preheated oven for 45 minutes.
After 30 minutes of baking, remove the baking tin carefully using oven mitts or a thick kitchen towel and pour 1/4 CUP of milk all over the cake and put it back to bake for 15 minutes.
Remove after 45 minutes or when a tester poked into the cake comes out clean.
Cool for 10 mins in the tin itself and cut into squares. Serve warm with a dusting of powdered sugar or vanilla custard or whipped cream.