Sponge cake(Biscuit de Savoie from "The Cake Bible," Rose Levy Beranbaum:
Preheat the oven to 325F. line 2 9-in. square ungreased pans.
8 large egg yolks
2/3 cup sugar
2 & 1/2 tsps. vanilla
1 tbsp. warm water
Beat the yolks and sugar on high speed until the mixture is very thick and ribbosn when dropped from the beater. Lower the speed and add vanilla and water. Increase to high speed and beat for 30 seconds until it thickens again.
1 cup + 2 Tbsps. sifted cake flour
1/2 cup + 1 tbsp. cornstarch
and then sift over the egg yolk mixture without mixing in and set aside.
Beat 8 egg whites until foamy and add 1 tsp. cream of tartar, and beat until soft peaks form when the beater is raised. Gradually beat in 1/3 cup sugar and beat until stiff peaks form when the beaters are raised.
Add 1/3 of the whites to the yolk-flour mixture and fold until incorporated. Gently fold in the rest of the egg whites.
Pour into prepared pans and bake for 25 minutes or until cake tester comes out clean. Loosen the sides w/ a small metal spatula and unmold at once onto lightly greased racks and reinvert to cool.