Preheat oven to 350°F.

Combine flour, sugar, baking powder, and salt in a mixer bowl. Add oil, egg yolks, citrus peels, and juice; beat until smooth.

In a separate bowl, beat egg whites until frothy. Add cream of tartar and beat until stiff peaks form. Pour yolk mixture in a thin, steady stream into beaten whites; fold in gently.

Pour into ungreased, 10-inch tube pan. Bake 55 minutes or until cake springs back when touched gently.

Immediately invert onto longnecked bottle to cool completely. Remove from pan and turn upright onto serving plate. Sprinkle with confectioners’ sugar.