Preheat oven to 180°C (160°C fan-forced). Lightly grease and line a 20cm x 20cm square brownie tin with baking paper.

Place beetroot in small saucepan covered in water, over a medium-high heat. Bring to boil and cook until tender.

Drain, allow to cool, before removing skin and cutting into chunks. Place beetroot chunks in a food processor and puree until smooth.

In a large mixing bowl, combine butter, chocolate, zest and sugar together over a saucepan of simmering water. Stir occasionally until mixture is melted and smooth.

Add pureed beetroot, eggs, flour, cocoa, cinnamon, ginger and walnuts, stirring until combined.

Pour mixture into prepared tin and bake in preheated oven for 30 minutes or until a skewer comes out of centre with moist crumbs.

Remove from oven and allow to cool completely before cutting.