Pre-heat oven to 220ºC
Add the bananas, buttermilk, coconut oil and vanilla to a food processor and process until it is smooth and creamy with no lumps.
With the processor still on, slowly add the flour, baking powder and baking soda and mix until it is fully combined.
Pour the batter into a lightly oiled doughnut tin.
Bake in the oven for 8-10 minutes or until the top of the doughnuts are golden, then remove from the oven and leave on a wire wrack until cooled enough to eat.
To decorate,, melt the additional coconut oil then using a pastry brush, lightly brush the tops and sides of the doughnuts until covered.
Mix the coconut sugar with the cinnamon then sprinkle over and eat!