Preheat the oven to 180°C/160°C fan/gas 4. Butter or oil a round non-stick cake tin (about 23cm in diameter) with a removable base.
Using an electric whisk, whisk the egg whites until soft peaks form.
In another bowl, using the same whisk, beat the egg yolks with the sugar until thick and pale. Add the flour, yoghurt, lemon zest and juice and beat to a homogenous cream.
Gently fold the egg whites into the yoghurt mixture and pour into the prepared tin. Bake for 40–45 minutes, until the top is lightly browned – watch it carefully for the last few minutes of cooking so that it doesn’t brown too much. The cake will puff up like a soufflé and then subside.
Let it cool a little before lifting it out onto a serving plate. Serve warm or cold.
For a beautiful accompaniment to the yoghurt cake, briefly rinse 500g strawberries, hull and cut them in half through the stem end, then sprinkle with 60g caster sugar and the juice of ½ lemon and leave for one hour.