First, preheat your oven to 170C/150C/Gas 3. Line the bottom of an 8-inch springform or high-sided 7-inch cake tin with baking paper, then grease the sides of the tin. Always line the bottom at least, because you can’t get there with a knife!
In a large bowl, beat your butter, zest and sugar together. I often use a wooden spoon, but you’ll find it easiest with an electric mixer. Keep going until the mix is white and mousse-like (the softer the butter, the quicker this will happen).
Add your eggs, one at a time, beating well after each addition. If you’ve only got large eggs, only add 2 and a half. Don’t worry if it curdles.
Once your eggs are mixed in, add your polenta, almonds and baking powder. Gently, fold these all in with a large spoon until completely combined, then scoop into your lined and greased tin.
Transfer to the middle shelf of your oven and bake for 25-35 minutes, or until a light golden brown. It should spring back when pressed and a skewer should come out clean. If it ends up sinking in the middle, try baking at a bit higher a temperature next time. Cool in the tin; you don’t need a cooling rack if you’ve lined it properly.
If you like, you’re done. But for a tangy twist, make a syrup by bringing to the boil in a pan your sugar and the juice from your two lemons. As soon as it’s bubbling furiously, remove from the heat. Use a knife or skewer to poke loads of holes in your still-hot cake, and then drizzle your syrup all over so that it soaks in easily.
You might not make this cake tough or chewy by overmixing it when you add the dry ingredients, but you can easily beat all the air that you’ve so carefully incorporated back out. Please, fold gently and carefully.