Preheat oven to 325°F.

In large bowl, sift flour, granulated sugar, baking powder and salt. Add oil, egg yolks, lemon juice, water and lemon zest; whisk until well combined. In large bowl, beat egg whites and cream of tarter with electric mixer to stiff peaks. Fold 1/3 of whipped whites into the batter to lighten. Gently fold in the remaining whites until mixture is combined; do not overmix or batter will deflate. Pour into ungreased pan; tap gently on counter to release air pockets.

Bake 50-60 minutes or until cake springs back when touched. Invert pan immediately after removing from oven; cool completely. Run knife around the sides and center of cake to loosen.

For glaze, combine butter, zest, confectioners' sugar, juice and vanilla in medium bowl; stir until smooth. Pour over cooled cake and spread with spatula. Glaze that drips off cake can be scooped back up with spatula. Glaze will set hard within 30 minutes.