1) Preheat the oven to 325°F. Have on hand an ungreased 10" tube pan.
2) Sift into a large mixing bowl the flour, baking powder, sugar, and salt.
3) Make a well in the center of the dry ingredients and add (in order) the oil, water, egg yolks, vanilla, grated lemon peel, and extract. Mix until smooth; scrape the bowl and mix for 30 seconds more.
4) In a separate bowl with clean beaters, combine the egg whites and cream of tartar or lemon juice. Whip until very stiff.
5) Fold one quarter of the beaten whites into the egg yolk mixture to lighten it up, then gradually (in four additions) pour the yolk mixture back over the remaining whites, folding gently just until blended each time. Pour the batter into the tube pan.
5) Bake the cake for 55 minutes, then increase the oven temperature to 350°F and bake for an additional 10 to 15 minutes, until a cake tester or toothpick inserted into the center comes out clean.
6) Remove the cake from the oven, and cool it upside down, inverted over the neck of a bottle.
7) When completely cool, run a thin-bladed metal spatula between the cake and the pan, and turn the cake out onto a serving plate. Garnish as desired.
Yield: One cake, 20 servings.