Preheat the oven to 170°C (340℉) or 150℃ fan (302℉) and grease or line a 12-pan muffin or cupcake pan. I usually get 10-11 cakes from this recipe. You can make it into a small 6-inch cake, just line and grease the tin. The baking time is around the same.
Peel and grate the beetroot into a large bowl. I peel and weigh my beetroot and then grate it leaving a small nub at the end to protect my fingers (I have a healthy fear of my box grater). Don't worry too much about it - I would say about 175g goes into the cake.
Add the remaining wet ingredients to the beetroot and mix well to combine.
To make the sunflower meal, pop the seeds in a blender or a small food processor. Blitz until you have the texture of almond meal.
In a separate bowl, combine the sunflower seed meal (or almond meal), buckwheat flour, cocoa powder, baking powder and salt.
Add the wet mixture to the dry.
Mix until combined and spoon evenly among the lined cake moulds - fill each around two-thirds of the way up.
Bake in the oven for 21 -24 minutes or until the sides of the cakes are pulling away and the top is domed. You should be able to gently push the top of the cake and have it given you resistance. If it feels too soft on the top, pop the cake in for another minute or two and check again.
Remove from the oven and allow to cool for 5 minutes before gently removing each cake out of the moulds to cook completely.