Wash and trim both ends of the rhubarb stalk. Cut the rhubarb into 1/2 inch chunks. If some of your stalks are very thick you can slice the whole thing in half. You want to make sure your rhubarb pieces are equally sized.
Preheat oven to 350 degrees Fahrenheit.
In a large bowl whisk the eggs. Let them come to room
temperature for a couple of minutes before adding the coconut
oil to avoid the hardening of the oil.
In the meantime, in another large bowl, combine all the dry
ingredients: Tigernut flour, cassava flour, arrowroot flour, coconut flour, salt, and baking soda. Mix thoroughly.
Add coconut milk, melted coconut oil, vanilla, and honey to the
egg mix and whisk until smooth. Combine with the flour mix
and whisk until you have a smooth/thick batter. Finally, fold in half of the rhubarb and make sure it is distributed evenly.
Grease a round 9-inch cake pan with coconut oil and flour it with arrowroot flour.
Pour the batter into the cake pan. Use a spoon to distribute it since it will be quite thick. Add the rest of the rhubarb evenly on top and slightly press it into the batter.
Bake for about 55 minutes or until a cake tester/toothpick
comes out without batter on it.
Let it cool off and right before serving dust with powdered
sugar using a sieve.