Good-Cooking - Chocolate Orange Angel Food Cake

Ingredients

• 1 1/2 cups powdered sugar
• 3/4 cup cake flour
• 1/4 cup cocoa
• 1 1/2 cups egg whites (about 12)
• 1 1/2 teaspoons cream of tartar
• 1 cup granulated sugar
• 1/4 teaspoon salt
• 3 cups orange sherbet, softened