“I first had Meyer lemons when I was working at Chez Panisse in Berkeley, California. They grow in people’s back gardens there, just like apple trees do in the UK, and are so plentiful you can barely give them away when they are in season, and there are always windfalls all over the street. Meyer lemons have a flavour that is best described as half mandarin, half lemon; just the right amount of sweetness and slightly tart. With lots of juice and little pith, they are the perfect citrus fruit. The skin is very thin, so the zest is easy to use, but this also means that the fruit don’t travel well. If you can’t get hold of them, simply combine both the juice and zest of a mandarin and an unwaxed lemon, which will give you something as close as possible to the flavour. ”
Preheat the oven to 200°C/180°C fan/400°F/Gas 6. Cream the butter and sugar together in a stand mixer fitted with the beater attachment, on medium speed for 3–5 minutes, until pale and fluffy. One at a time, add the eggs, mixing well between each addition. Gradually add the flour and baking powder, about a third at a time, until fully incorporated, then mix in the lemon zest and juice. Mix until fully combined, but take care not to overmix.
Grease a 20cm (8in) springform cake tin with butter and line the base with baking paper. Pour in the sponge mixture and bake for 40 minutes, until a skewer inserted into the centre of the cake comes out clean. Remove the cake from the tin and place it on a wire rack to cool while you make the icing.
Sift the icing (confectioner’s) sugar into a bowl and add the lemon zest and juice. Using a hand-held electric whisk, whisk thoroughly until the icing is really smooth. Pour the icing over the top of the cooled cake in an even layer, then leave it to set for 1 hour. Serve in slices with a cup of tea.