Preheat oven to 170°C (338°F) and line 2 x 22 cm (9-inch) pans with grease-proof or baking paper.
Combine the milk and apple cider vinegar in a mixing bowl and set aside.
In a large mixing bowl mix together the flours, baking soda, baking powder, sea salt, cocoa powder and sugar.
Gently whisk the sunflower oil and vanilla extract in to the milk/vinegar (buttermilk) mixture.
Add wet ingredients to the dry ingredients and lightly whisk before adding the boiling water and whisking gently until combined. Be careful whisking the boiling water.
The batter is thin so I pour it in to a large pouring jug and distribute it evenly between the cake pans - up to around ¾ of the pan height.
Pop the pans in the oven and bake for 28-33 mins or until a skewer comes away from the centre cleanly.
Remove from the oven and sit the cakes for 10 minutes before turning them out to cool completely.
Place one cake, flat side up, and top with your favourite frosting. Place the second cake on top, add more frosting and decorate with fresh fruit to serve.