Peel and roughly chop the beetroot and place in a medium sized bowl. Add a splash of water and cover with glad wrap, then microwave on high for 12 minutes or until the beetroot is tender.
Preheat the oven to 180C and line a square brownie tin.
Tip the cooked beetroot into a sieve and drain away any excess liquid. Blitz the beetroot in a food processor with the chocolate, butter and vanilla until smooth
Beat together the sugar and butter in a large bowl until pale and foamy. Add the beetroot mixture one scoop at a time and fold until all is combined.
Sift the flour and cocoa powder into the wet mixture and fold until you have a smooth batter.
Pour the batter into your brownie tin and bake for 25 minutes.
Set aside and let cool on a wire rack before cutting into squares.