Hungarian Sponge Cake

1 cup sifted cake flour
1 ¼ teaspoons baking powder
6 eggs, separated
1 cup sugar
7 tablespoons cold water
1 teaspoon vanilla
pinch slat
1 teaspoon cream of tartar

Sift flour and baking powder 3 or 4 times. Beat egg yolks and sugar, at medium speed, 5 minutes until thick and light in color. Gradually add water and vanilla. Beat egg whites, salt and cream of tartar until stiff peaks form. Fold into egg yolks, alternating with the cake flour. Pour into two 8 inch pans, greased on the bottoms only. Bake in a 350 degree oven 35 minutes. Cool upside down. Put layers together with custard filling between them. Sprinkle the top with extra confectioners sugar.
Custard Filling:
½ cup flour
¾ cup sugar
pinch salt
1 egg, beaten
1 cup milk
1 teaspoon vanilla
4 ounces margarine, softened
3 tablespoons confectioners sugar

Measure flour, sugar, and salt into a sauce pan. Add egg and a little milk; stir to form a soft paste. Blend in remaining milk. Cook over low heat until thick, stirring constantly. Remove from heat and beat in vanilla. Set aside to cool completely. Add margarine and confectioners sugar. Beat until fluffy.