Preheat oven to 325 °F. Sift together flour, 1 cup of the sugar, baking powder and salt into a medium mixing bowl.
Make a well in center of flour mixture; add oil, egg yolks, orange rind and orange juice. Beat with paddle attachment of electric mixer until smooth.
In a large mixing bowl, whip egg whites with cream of tartar until frothy. Add remaining 1/2 cup sugar in four additions, beating until stiff, but not dry peaks form.
Pour egg yolk mixture gradually over egg whites, folding gently just until blended.
Pour into ungreased 10-inch tube pan and bake for 65 minutes. Invert pan over a long -necked bottle to cool. Brush with Cointreau Syrup. Yields 12-15 servings.