In a large bowl mash a banana using a fork. Then add soy milk, lemon juice, sugar, and vanilla. Combine and add oat flour, cassava flour, baking powder, and baking soda.
Create a smooth dough. It should be similar to a pancake batter, maybe a little thicker.
Pour the dough onto a baking sheet lined with baking paper and bake at 400F (200°C) for about 30 minutes.
When the cake is baked, cool it down, and in the meanwhile let's prepare the coconut frosting.
In a blender add shredded coconut and blend it into a flour-like consistency.
In a large bowl whisk margarine with sugar until creamy and fluffy. Add coconut cream and blended coconut. Whisk with a hand mixer until combined.
When the cake has cooled down, it is ready to assemble with the frosting.
Cut the cake vertically into 3 long strips. Spread the coconut cream onto the first layer and add the second layer of cake. Then add a layer of coconut frosting and the last layer of the cake. Cover the cake with the frosting and extra shredded coconut.
Put the cake into the fridge for about 1 hour before serving. Enjoy!