Place egg whites in a large bowl; let stand at room temperature 30 minutes. Sift 1/2 cup sugar and flour together twice; set aside. , Place oven rack in the lowest position. Preheat oven to 350°. Add cream of tartar, extracts and salt to egg whites; beat on medium speed until soft peaks form. Gradually add remaining sugar, about 2 tablespoons at a time, beating on high until stiff peaks form. Gradually fold in flour mixture, about 1/2 cup at a time., Gently spoon into an ungreased 10-in. tube pan. Cut through batter with a knife to remove air pockets. Bake until lightly browned and entire top appears dry, 35-40 minutes. Immediately invert pan; cool completely, about 1 hour. , Run a knife around side and center tube of pan. Remove cake to a serving plate.