Preheat the oven to 180°C.
Grease a 20cm nonstick cake tin with a little Spray and Cook and line the bottom of the tin with baking paper.
Purée the beetroot in a food processor.
Heat the butter and chocolate in a microwave for 10 seconds at a time, or until just melted, then pour in the hot coffee and leave to cool slightly.
Sift the flour, baking powder and cocoa in a bowl and set aside.
Separate the eggs, then whisk the yolks in a bowl until frothy.
Stir the eggs into the chocolate and butter mixture and fold in the beetroot.
Whisk the egg whites until stiff peaks form, then fold in the sugar.
Fold the sugar and egg whites into the chocolate mixture, then fold in the flour and cocoa mixture.
Pour the batter into the tin and bake for 40 to 45 minutes, or until a skewer inserted into the cake comes out clean.