Step 1

Preheat the oven to 350° and grease a 9" round cake pan.

Step 2

Beat together the egg yolks and the sugar.  Ad in the sifted flour, the yogurt, the zest and juice of the lemon, and mix all the ingredients thoroughly together.

Step 3

Whisk the egg whites until stiff and fold them into the yogurt batter.

Step 4

Pour the batter into the prepared cake pan and bake in a preheated oven for 50 to 60 minutes until the top is brown.  It will puff up like a souffle and then subside.

Step 5

When completely cooled, dust with confectioner's sugar.