Flourless Walnut Cake
Beat the egg yolks and sugar together until light and fluffy, about 4 minutes with an electric mixer.
Stir in lemon zest.
In a separate bowl, beat egg whites until stiff.
Fold a quarter of the whites into the egg mixture to loosen it.
Stir walnuts into mixture until thoroughly blended.
Fold in remaining egg whites carefully to maintain light texture.
Cool cake on a rack before turning out and then alternately dust with Powdered sugar and cocoa.