Chocolate Angel Food Cake 2
Source: Whitman's Chocolate Cookbook

1 cup all-purpose flour
1 1/2 teaspoons cream of tartar
1/4 cup cocoa
1/2 teaspoon salt
1 1/2 cups sugar
1 1/2 teaspoons vanilla
10 egg whites

Preheat oven to 325 degrees F.

In medium bowl, sift flour. Sift flour again twice with cocoa and 1/2 cup sugar. Set aside. In large bowl, beat egg whites, cream of tartar, and salt until soft peaks form. Gradually add remaining sugar, 2 Tbsp at a time until stiff peaks form. Fold in flour mixture and vanilla.

Pour into ungreased tube pan. Bake for 55 to 65 minutes. Invert pan for about 1 hour or until the cake is cool.