Place the egg whites in a large bowl; let stand at room temperature for 30 minutes. Meanwhile, line a 15-inch x 10-inch x 1-inch baking pan with waxed paper; lightly coat paper with cooking spray and set aside.

Add vanilla and cream of tartar to egg whites; beat on medium speed until soft peaks form. Gradually beat in sugar, 2 tablespoons at a time, on high until stiff shiny peaks form and sugar is dissolved. Fold in flour, about 1/4 cup at a time.

Carefully spread batter into prepared pan. Bake at 350°F for 15 to 20 minutes or until cake springs back when lightly touched. Cool for 5 minutes.

Turn cake onto a kitchen towel dusted with 1 tablespoon confectioners’ sugar. Gently peel off waxed paper. Roll up cake in the towel jelly-roll style, starting with a brief side. Cool fully on a wire rack.

In a large saucepan, combine sugar and cornstarch; stir in water until smooth. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat; cook and stir 2 minutes longer. Remove from the heat. Stir a small amount of hot mixture into egg; return all to the pan, stirring continuously. Bring to a gentle boil; cook and stir 2 minutes longer.

Remove from the heat. Gently stir in lemon juice, peel and food coloring if desired. Cool to room temperature without stirring.

Unroll cake; spread filling to within 1/2 in. of edges. Roll up again. Place seam side down on a serving plate; sprinkle with additional confectioners’ sugar.