Preheat the oven to 180C/Fan160C/Gas Mark 4. Grease and line the base and sides of a 20cm x 20cm cake tin with baking parchment and grease again. Dust the base and sides with flour. Remove any excess flour.
Place the beetroot in a liquidiser or food processor and whizz until smooth.
To melt the chocolate, bring a saucepan of water to the boil. Place the chocolate with the butter in a large heatproof bowl. Once the water is boiling turn the heat off and place the bowl on top of the saucepan. Allow the chocolate and butter to melt stirring from time to time. Once melted remove from the heat and set aside.
Place the sugar and eggs in a bowl and whisk until light and creamy about 3-4 minutes. Stir in the beetroot mixture and melted chocolate. Add the cocoa, flour and baking powder. Stir with a metal spoon to combine. Spoon the batter into the cake tin and bake in the centre of the oven for 35-40 minutes. Cool completely in the tin.
Remove the brownies from the tin. Mix the icing sugar with 2 tsp cold water. Add enough pink food gel to your colour liking and mix again until smooth. Use a teaspoon to drizzle the icing over the brownies. Allow the icing to set. Sprinkle with raspberry powder, if using. Cut into 9 brownies.