Preheat the oven to 160°C (fan 140°C, gas mark 3). Grease a 20cm round cake tin with a little coconut oil and line the base with baking parchment.
Mix the self-raising flour, ground almonds, vanilla protein powder, baking powder, bicarbonate of soda and a pinch of salt in a large bowl.
In a separate bowl, whisk the cocoa powder with 150ml boiling water until well combined, then whisk in the melted coconut oil, maple syrup, coconut milk and orange zest.
Pour the wet ingredients into the dry and give everything a good whisk until you have a smooth runny batter. Pour into the cake tin and bake for 35 minutes or until a skewer inserted into the centre of the cake comes out clean.
Cool in the tin. When cool, dust with a little cocoa powder and serve topped with coconut yoghurt and berries if you like.
Keep in an airtight container for up to 3 days.
When cooled, cover well and keep in the freezer for up to 1 month.
Veggie Lean in 15 by Joe Wicks is out now (Bluebird)