Lightly grease 15 ½ x 10 ½ x 1-inch jelly roll pan. Line bottom with waxed paper. Grease again. Set aside.
In large mixing bowl, beat egg whites with cream of tartar at high speed until foamy. Add ⅓ cup of the sugar, 2 tablespoons at a time, beating constantly until sugar is dissolved and whites are glossy and stand in soft peaks. (Rub just a bit of meringue between thumb and forefinger to feel if sugar has dissolved.)
In small mixing bowl at high speed, beat egg yolks until thick and lemon-colored. Gradually beat in remaining ⅓ cup sugar, vanilla and salt until blended.
Sprinkle flour over whites. Add beaten yolk mixture. Gently, but thoroughly, fold yolk mixture and flour into whites. Pour into prepared pan. Gently spread evenly.
Bake in preheated 400° F oven until top springs back when lightly touched with finger, about 10 to 12 minutes.
Dust clean tea towel with confectioners’ sugar. With spatula, loosen cake from sides of pan and invert onto prepared towel. Carefully pull waxed paper off bottom of cake. Trim all edges with serrated knife. Starting from short edge, roll up cake, rolling towel in with cake. Place wrapped roll seam-side down on wire rack until cool, about 30 minutes.
Carefully unroll cake and spread with whipped cream. Reroll. Place seam-side down on serving platter.Cover and chill.