Preheat the oven to 180C/350F and line a 23cm square tin with baking parchment.
Break the chocolate up into small pieces and melt it in a metal bowl over simmering water, ensuring the water doesn't touch the bowl. Remove just before fully melted and stir.
Whizz up the beetroot until it’s a puree.
In a large bowl, whisk together the olive oil and sugar, then add the slightly cooled chocolate and beetroot, followed by the eggs.
Add the ground almonds, baking powder, salt, and cocoa, and mix well.
Pour the mixture into the tin, smooth it out, and top with flaked almonds.
Bake for 45 minutes.
