Separate eggs. Allow egg whites and yolks to stand at room temperature for 30 minutes. Meanwhile, grease a 15x10x1-inch baking pan. Line bottom of pan with waxed paper or parchment paper; grease paper. Set pan aside. In a medium bowl stir together flour, cocoa powder, and baking powder; set aside.

Preheat oven to 375°F. In a medium mixing bowl beat egg yolks and 1/2 teaspoon vanilla with an electric mixer on high speed about 5 minutes or until thick and lemon color. Gradually add 1/3 cup granulated sugar, beating on high speed until sugar is almost dissolved. Beat in food coloring.

Thoroughly wash beaters. In another mixing bowl beat egg whites on medium speed until soft peaks form (tips curl). Gradually add 1/2 cup granulated sugar, beating until stiff peaks form (tips stand straight). Fold egg yolk mixture into beaten egg whites. Sprinkle flour mixture over egg mixture; fold in gently just until combined. Spread batter evenly in the prepared baking pan.

Bake for 12 to 15 minutes or until cake springs back when lightly touched. Immediately loosen edges of cake from pan and turn cake out onto a clean kitchen towel sprinkled with powdered sugar. Remove waxed paper. Roll towel and cake into a spiral, starting from a short side of the cake. Cool on a wire rack.

For filling, in a medium bowl fold together dessert topping, sour cream, and 1/2 teaspoon vanilla. Unroll cake; remove towel. Spread cake with filling to within 1 inch of the edges. Roll up cake; trim ends. Cover and chill for up to 6 hours. Sprinkle cake with additional powdered sugar.