Separate the egg whites from the egg yolks.
In a salad bowl, whip the yellows with sugar until the mixture becomes white.
Add the yogurt, oil, and mix well.
Add the flour and yeast sift little by little. Add zest of lemon or vanilla if desired.
Ride the Snow White:

Add a pinch of salt to the egg whites and mount in solid snow.
Gently incorporate the raised whites into the preparation by raising the batter to keep maximum air.
Cooking:

Pour batter into mold and bake for 30-35 minutes. Check the cooking by planting a knife blade in the center: it must come out dry.
Let cool and serve:

Once baked, let cake cool before rolling it out. Sprinkle icing sugar for the finishing touch.
Tips:

For an even more airy version, use Greek yogurt.
Accompany a red fruit coulis or a compote for a refined dessert.