German Oven Pancake II

Preheat oven to 400. Place 2 tbsp. butter in a 9 x 9 pan and place in oven to melt. Mix egg yolks, cornstarch, milk, sugar, and lemon rind together thoroughly. Beat egg whites until they hold stiff peaks. Gently fold these into the batter. Pour batter into pan and bake for 7-10 minutes.