Heat oven to 325 degrees. In a large bowl, combine flour, baking powder, and salt; mix in well. Add water, oil, egg yolks, and vanilla; beat on low speed until moistened. Beat at high speed for 5 minutes until very smooth, scraping sides of bowl occasionally. Fold in grated lemon peel. Clean the beaters well. In another large bowl, combine egg whites and cream of tartar; beat 3 minutes until stiff peaks form. Gradually add egg yolk mixture to egg whites, folding gently to combine. Pour into ungreased 10-inch tube pan. Bake at 325 degrees for 60 to 75 minutes or until top springs back when lightly touched. Immediately invert cake onto funnel or soft drink bottle. Let hang for 1 hour to completely cool. To remove cake from pan, run edge of knife around outer edge of pan and tube.