Preheat oven to 180 degrees and grease skillet with butter or extra coconut oil.
Chop two apples into chunks and the remaining one into slices to top the cake. Toss the apple in the lemon juice to stop it from browning. Keep the slices to one side.
Mix together all the dry ingredients and whisk to ensure there is no lumps. Mix together wet ingredients and and whisk to incorporate. Blend the two together and fold in the apple chunks. Do not overmix. Once combined spoon into prepared pan and smooth with the back of a wet spoon. Top cake with the reserved apples to decorate.
Bake in the oven for 35-40 minutes or until bounces back when pressed lightly.