In a medium bowl, whip the egg yolks and half of the sugar with an electric mixer until thick and pale. Set aside. In a separate larger bowl, combine the egg whites and vanilla. Whip with clean beaters until foamy. Gradually sprinkle in the remaining sugar while continuing to whip until stiff but not blocky. Fold the yolks into the whites by hand, then fold in the dry ingredients. Spread evenly in the prepared pan.