Preheat oven to 325 degrees.
In a large bowl with mixer at high speed, beat egg whites and cream of tartar until soft peaks form. Beating at high speed, gradually sprinkle in 1/2 cup sugar, 2 tablespoons at a time, beating until each addition is completely dissolved. Do not scrape sides of bowl at any time.
Whites should stand in stiff peaks. Set aside.
In a large bowl with mixer at high speed, beat egg yolks until thick and lemon colored. Continue beating, gradually sprinkling in 1/2 cup sugar; beat until pale yellow. Reduce to low speed; add flour, 1/4 cup orange juice, baking powder and salt until well mixed, occasionally scraping bowl with spatula. Using a spatula, fold the egg white mixture into the yolk mixture until just blended.
Line 2, 9 inch round cake pans with waxed paper; do not grease. Pour batter into pans and bake for 40 minutes or until cake springs back when lightly touched. Cool cakes in pans on wire racks for 10 minutes. Remove cakes from pans and cool completely on racks. With fork, prick holes in cake layers.
In a small saucepan over medium heat, boil 1/3 cup water, and the remaining 1/4 cup sugar for 3 minutes. Stir in the remaining 1/2 cup orange juice. Drizzle evenly over layers and let stand for 30 minutes.
In a small bowl, with mixer at medium speed, beat cream and powdered sugar until soft peaks form. Fold in orange peel.
Place one layer on serving platter and spread with 1/3 of whipped cream. Top with second layer. Frost top and sides with remaining cream. Garnish with orange sections or candied orange peel and fresh mint sprigs. Refrigerate.
For best results in whipping cream, chill the bowl and the beaters beforehand.
For a variation on the orange cake, spread a thinlayer of marmalade between the layers.
Dr. White also calls this cake "waxed paper" cake and warns not to forget to remove the waxed paper before icing, as he once did.
c.1997, M.S. Milliken & S. Feniger, all rights reserved