Courtesy of Pinterest
Preheat oven 180°
Sift flour, sugar, baking powder and salt together twice; place in another large bowl. In a small bowl, whisk egg yolks, water, oil, lemon zest and vanilla until smooth. Add to flour mixture; beat until well blended.
Add cream of tartar to egg whites; with clean beaters, beat on medium speed just until stiff but not dry. Fold a fourth of the whites into batter, then fold in remaining whites.