Preheat the oven to 325°F. Put the rack in the lower half of the oven.

Sift together into a bowl the flour, sugar, baking powder and salt.

Make a well in the center of the flour mixture and add the oil, egg yolks, lemon rind, water and vanilla. Stir and beat until smooth.

In another bowl beat the egg whites with the cream of tartar until very stiff, much stiffer than for meringue.

Pour the egg yolk mixture gradually over egg whites, folding gently with a rubber spatula until just blended. Do not stir.

Pour the batter at once into an ungreased 10-inch tube pan. Bake for 65 to 70 minutes.

Immediately turn the tube pan upside down and place the tube over a funnel or other support so that the cake can hang in the pan free of the table until cool.

To remove cake from pan, loosen it from the tube and sides with a spatula and hit the edge of the pan on the table. Serve plain or top with orange or lemon glaze.