Preheat your oven to 175°C fan.
Grease and line a 23cm springform cake tin.
In a large bowl, add the sugar and lemon zest, and rub them together with your fingertips to release the oils — it makes such a difference to the flavour.
Whisk in the eggs and oil for 4–5 minutes until light and fluffy.
Sift in the flour, baking powder and salt, then fold through gently.
Add the Greek yoghurt and lemon juice, and fold again until just combined — don’t overmix, and try not to knock out that lovely air.
Pour the mixture into your prepared tin and bake for 25 minutes, or until golden and just springy to touch.
Let the cake cool completely before decorating.
In a heatproof bowl over a gentle bain-marie, whisk the egg whites, sugar and lemon zest until the sugar has dissolved and the mixture feels smooth between your fingers.
Remove from the heat and whip until thick, glossy and cloud-like.
In a small saucepan over low heat, whisk together the yolks, sugar, lemon juice and zest.
Stir constantly until it thickens into a smooth, glossy curd.
Remove from heat, whisk in the butter, and let cool.
Once the cake is completely cool, spoon the Swiss meringue on top and swirl it into soft peaks.
Dot with lemon curd, and use a skewer or spoon to gently swirl it through.
Finish with a final dusting of fresh lemon zest — it brings the whole thing to life.