1/3 cup cocoa
1/4 cup hot water
1 1/2 cups plus 3 tablespoons granulated sugar - divided use
2 tablespoons plus 1/2 cup vegetable oil - divided use
2 1/4 cups all-purpose flour
3 teaspoons baking powder
1 teaspoon salt
3/4 cup cold water
7 large egg yolks
1 cup (about 8) large egg whites
1/2 teaspoon cream of tartar
1 tablespoon freshly grated orange peel
1/3 cup butter or margarine
2 cups powdered sugar
2-3 tablespoons orange juice
1/2 teaspoon orange peel
Preheat oven to 325°F (160°C).
In a medium bowl, stir together cocoa and hot water. Add in 3 tablespoons sugar and 2 tablespoons oil and mix; set aside.
Combine flour, remaining 1 1/2 cups sugar, baking powder and salt in large bowl; add cold water, remaining 1/2 cup oil and egg yolks; beat with spoon until smooth.
In another bowl, beat egg whites and cream of tartar using an electric mixer on high speed until stiff peaks form. Pour egg yolk mixture in a thin stream over beaten whites, gently folding just until blended.
Add two cups of the batter into chocolate mixture, gently folding in until well blended. Fold orange peel into remaining batter.
Spoon half of orange batter into ungreased 10-inch tube pan; drop half the chocolate batter on top by spoonfuls. Repeat layers of orange and chocolate batters. Gently swirl with knife for marbled effect, leaving definite orange and chocolate areas.
Bake for 1 hour and 15 to 20 minutes or until top springs back when touched lightly. Immediately invert cake in pan onto heatproof funnel; cool completely. Remove cake from pan; invert onto serving plate.
Meanwhile, prepare the Orange Glaze: Melt the butter or margarine in medium saucepan over low heat. Remove from heat; gradually add powdered sugar, orange juice and freshly grated orange peel, beating with whisk until smooth and of desired consistency.
Pour glaze over top of cake, allowing it to run down the sides.