Preheat oven to 325 degrees. Place cocoa in a small bowl. Add boiling water, stirring until smooth. Let mixture cool. In a second bowl, sift flour with sugar, soda and salt. Make a well in center; pour liquid butter Buds, Egg Beaters, vanilla and cooled cocoa. With electric mixer, beat until smooth. Sprinkle cream of tartar over egg whites. Beat at high speed, until stiff peaks form. Do not overbeat. Pour batter over egg whites. Gently fold into egg whites until just blended. Turn batter into a 25 cm tube pan. Bake 65-70 minutes. Invert pan over neck of bottle; let cool completely, about 1.5 hours.
Per serving: Calories, 178, Fat 0.15g, Choles 0mg, Sodium 50mg.