Two Part Angel Cake - cooking recipe

Ingredients

6 egg whites
1/2 teaspoon cream of tartar
1/4 teaspoon salt
3/4 cup white sugar
1/2 cup all-purpose flour
1/2 teaspoon vanilla extract
6 egg yolks
3/4 cup white sugar
1/4 teaspoon salt
3/4 cup all-purpose flour
1/4 cup boiling water
3/4 teaspoon baking powder
1 teaspoon vanilla extract

Preparation

To make Bottom/White part: Beat whites with salt until frothy. Add cream of tartar and continue beating until stiff, but not dry. Sift 1/2 cup flour and 3/4 cup sugar 4 times (separately). Add sugar gradually, then fold in flour. Add in 1/2 teaspoon vanilla. Put into ungreased angel cake pan. Prepare top.
To Make Top/Yellow Part: Beat yolks until light. Add 3/4 cup sugar, which has been sifted 4 times, gradually. Beat for 3 minutes. Add 3/4 cup flour and baking powder, which has been sifted together 4 times. Alternate flour mixture with hot water. Add 1 teaspoon vanilla. Pour this mix over top of first batter.
Bake at 325 degrees F (165 degrees C) for 40 minutes.