Lemon Chiffon Cake

Lemon Chiffon Cake 7 large eggs, separated 2 cups all-purpose flour 1-1/2 cups sugar 3 teaspoons baking powder 1 teaspoon salt 3/4 cup water 1/2 cup canola oil 4 teaspoons grated lemon peel 2 teaspoons vanilla extract 1/2 teaspoon cream of tartar FROSTING: 1/3 cup butter, softened 3 cups confectioners' sugar 4-1/2 teaspoons grated lemon peel 1/4 cup lemon juice Dash salt Place egg whites in a large bowl; let stand at room temperature 30 minutes. Meanwhile, preheat oven to 325°. Sift flour, sugar, baking powder and salt together twice; place in another large bowl. In a small bowl, whisk egg yolks, water, oil, lemon peel 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. Gently spoon batter into an ungreased 10-in. tube pan. Cut through batter with a knife to remove air pockets. Bake on lowest oven rack 50-55 minutes or until top springs back when lightly touched. Immediately invert pan; cool completely in pan, about 1 hour. Run a knife around sides and center tube of pan. Remove cake to a serving plate. In a small bowl, combine frosting ingredients; beat until smooth. Spread over cake.