Start by cleaning the lemons thoroughly, ensuring no dirt remains on the rind. Remove any stems if attached. In a small saucepan, pour in about 4 cups of water, then place the whole lemons in it. Bring the water to a gentle simmer over medium heat, allowing the lemons to cook for around 30 minutes. The lemons are ready when you can effortlessly pierce the rind with a fork. Drain the water, then set the lemons aside to cool completely.

Once cooled, chop the lemons roughly and discard any seeds. Transfer the chopped lemons into a food processor and blend until they reach a chunky consistency, with small visible pieces of the rind.

Preheat your oven to 170°C (340°F). Grease an 8-inch (20 cm) cake pan or line it with parchment paper to prevent sticking.

Next, add the remaining cake ingredients—almond flour, sugar, potato starch, water, baking powder, and turmeric—into the food processor with the lemon mixture. Blend everything until it forms a thick batter, similar in texture to a dense rice pudding. If the batter appears too loose, incorporate additional potato starch, one tablespoon at a time, until it thickens. A slightly thicker batter will yield the best result (note 4).

Pour the prepared batter into your cake tin, spreading it evenly with a spatula for a smooth surface.

Bake the cake in the preheated oven for 35-40 minutes. It's done when a toothpick inserted into the center comes out clean, with only a few crumbs attached but no wet batter. Once baked, let the cake cool completely in the tin before removing it.

For serving, you can sprinkle the top with a light dusting of icing sugar (note 5). Leftovers can be kept in an airtight container at room temperature for up to 1 day, in the fridge for up to 3 days, or frozen for up to 1 month.