6oz/175g unsalted butter, softened

8oz/225g caster sugar

7oz/200g ground almonds

3 large eggs

Zest of 4 whole lemons and juice of 1

4oz/115g polenta

1 tsp baking powder

Pinch of salt

* Preheat the oven to 325F/160C/gas mark 3. Line an 8" (20cm) tin with baking parchment.

* Put all the ingredients in a food processor and whizz to a smooth batter.

* Spoon into the lined tin and bake for 45-50 minutes, until a skewer pushed into the centre comes out with no uncooked batter on it. Cool in the tin.