Heat the oven to 160°C/gas 3.

Lightly butter a 20 cm pie dish.

Cream together the butter and caster sugar with an electric whisk until soft and smooth. Finely grate the lemon zest from two and a half of the lemons and then juice them. Add the zest and juice to the cake mix and blend.

Thinly slice the remaining half a lemon and keep on one side.

Beat the eggs into the cake mix -it will split, but do not worry, this is normal. Then beat in the polenta and ground almonds. Finally, fold in the flour with a large spoon.

Transfer the cake mix to the buttered dish, arrange the lemon slices on top and bake for 25-30 minutes. Serve warm, with cream.