Feather Sponge Cake
["6 egg yolks", "1/2 c. cold water", "1 1/2 c. sugar", "1/2 tsp. each: vanilla and lemon flavor", "1 1/2 c. sifted cake flour", "1/4 tsp. salt", "6 egg whites", "3/4 tsp. cream of tartar"]
["Beat egg yolks until thick and lemon colored.", "Add cold water. Beat until very thick.", "Gradually beat in sugar, then add vanilla and lemon flavor.", "Sift flour with salt.", "Fold into yolk mixture, a little at a time."]
["egg yolks", "cold water", "sugar", "vanilla", "cake flour", "salt", "egg whites", "cream of tartar"]