Good-Cooking - Raspberry Chocolate Chiffon Cake

Ingredients

• 1/2 cup cocoa
• 3/4 cup boiling water
• 1 3/4 cups cake flour
• 1 3/4 cups granulated sugar
• 1 1/2 teaspoons baking soda
• 1 teaspoon salt
• 1/2 cup vegetable oil
• 2 teaspoons vanilla extract
• 7 egg yolks
• 1 cup egg whites (7 to 8)
• 1/2 teaspoon cream of tartar
• 4 cups frozen whipped cream, thawed