Preheat the oven to 200°C (390°F) using the fan-assisted setting.
Combine the dry ingredients in a bowl: the flour, baking powder, sugar, and zest from the two lemons.
Mix the ingredients by hand, rubbing the lemon zest between your fingers to release its oils and enhance the flavor.
Add the lemon juice, making sure to remove any seeds.
Add the eggs and mix everything well.
Grease a baking tray with oil, place a sheet of parchment paper on top, and grease the paper as well.
Pour the batter into the tray.
Bring water to a boil in a kettle.
Place the baking tray with the batter on the oven tray and pour the boiling water into the oven tray. The water should reach about halfway up the sides of the baking tray.
Bake for 20 to 25 minutes in a water bath, until the cake is spongy but fully cooked.
Refrigerate overnight and serve the next day.
You can decorate it with a few lemon slices.