Preparation / Directions:
In a small mixer bowl, stir together flour, sugar, baking powder and salt. Make a well in the center; in order, add oil, egg yolks, peel and juice. Beat smooth with an electric mixer. Wash beaters, and in a large bowl, beat egg whites with cream of tartar until stiff. Gradually pour flour mixture (it will be stiff) in a thin stream over surface, and fold in gently. Bake in a 10" ungreased tube pan for 55 minutes at 350~, or until when lightly touched with the finger, the cake springs back. Invert. Cool completely. Loosen edges, and remove to a cake plate.
GLAZE: Mix all ingredients together, using enough grapefruit juice to make it spread easily, and drizzle down the sides when spread on top of the cake.