This is a classic cake that works well as an afternoon snack but even better as a dessert served with a spoonful of mascarpone or crème fraîche spiked with vanilla seeds. The almonds give the cake a moistness you just don’t get with flour, and the polenta contributes a slight crunch as well as a rich yellow color.
Preheat the oven to 350°F. Butter a 9-inch round cake pan and line with wax paper.
Mix the polenta, baking powder, salt, and almond flour in a bowl and set aside.
Using an electric mixer or wooden spoon, beat together the butter and 1 cup of the sugar for 5–10 minutes until light and fluffy. Lightly beat the eggs, then beat them into the butter mixture a spoonful at a time, making sure it is well incorporated before adding the next spoonful. (If the mixture looks like it’s splitting, beat in a spoonful of the polenta mixture before continuing with the eggs.)
When the eggs have been combined, beat in the polenta mixture. Finally, add the lemon zest and the juice of 1 lemon.
Bake in the preheated oven for 40–60 minutes until golden brown and just firm to the touch. To test if the cake is cooked, insert a knife or metal skewer into the middle: it should come out clean and the edge of the cake should come away easily from the side of the pan. Remove from the oven and leave to cool in the pan.
Make a syrup by heating the remaining lemon juice and sugar with the vanilla pod in a saucepan until the sugar has dissolved. Remove the vanilla pod and save for another use. Prick the top of the cake with a fork and pour the syrup over it. Leave to cool completely before turning out of the pan.