Heat the oven to 180C/ 160C fan/ gas 4 and line a 20cm x 20cm baking tin with baking parchment. Melt the dark chocolate with the butter in the microwave or in a heatproof bowl over just simmering water.
Mix together the sugar, flour and cocoa powder and stir in the melted chocolate and butter mixture, followed by the eggs. Stir through the dried cranberries and macadamia nuts, then swirl through the cranberry sauce.
Pour into the tin and smooth the surface. Bake for 25 - 30 mins. Allow to cool before slicing.