Preheat the oven to 180 degrees C (350 degrees F).
In a large mixing bowl, whisk together the buckwheat flour, rice flour, sugar, xanthan gum, baking powder and salt.
In a separate bowl, whisk together the dark chocolate, plant based milk, olive oil, flax eggs, lemon juice and cooked beetroot.
Add the wet ingredients to the dry and mix until thoroughly combined.
Transfer the batter to a 10-inch cake tin and bake in the preheated oven for 40 minutes, until a toothpick comes out clean from the centre.
MAKE THE FROSTING
In a large mixing bowl, use an electric mixer to whisk together the vegan cream cheese and butter.
Slowly sift in the icing sugar around ½ cup at a time, whisking it using the electric mixer. Add more icing sugar if the frosting is too moist.
Leave in the freezer for around 20 minutes.
ASSEMBLE THE CAKE
Make sure that the cake sponge cools down fully before assembling and adding the frosting.
Use a large chef’s knife to carefully slice the cake sponge in half.
Apply a thick layer of the frosting on top of one of the resulting sponges. Then, add the other cake sponge and add another frosting layer on top of the cake. If you wish, you can also add it around the sides.
You make 4 flax eggs by stirring together 4 tbsp ground flaxseed and 8 tbsp water and then setting it aside for 5 minutes.
You can either cook your own beetroot by boiling it, or buy it pre-cooked from the supermarket.