• Preheat the oven to 350F/175C and lightly grease an 8in cake pan.
• Peel, core and dice the apple and place in a small pan with the water. Bring to a boil and simmer for around 5-10mins until the apple is soft but not falling apart. Drain the water from the pan and mash the apple either by hand or in a food processor (if the latter, leave it in as there are other things to add).
• In a large bowl, mix together the flours, baking powder and soda, cinnamon and salt.
• Blend together the butter, coconut oil, eggs, vanilla, sour cream, milk, honey and maple syrup until smooth. You can either do this by hand or add all to the food processor with the apple.
• Add all of the wet ingredients to the flour mixture and mix well but try not to overmix. Pour the mixture into the cake pan and smooth the top. Bake for approx 45min until lightly brown all over and a skewer put into the center comes out clean.
• Allow to cool before icing.

For the buttercream/frosting

• Beat the butter either in a stand mixer or with a blender then add the sugar gradually until all is mixed in. Add the vanilla and mix in. Spread over the top of the cake or cut the cake through the middle and spread on one side before replacing the top. Chill until ready to serve.