Preheat the oven to 300 degrees F (150 degrees C) and lightly coat a 10x15-inch baking pan with nonstick spray. Line the bottom of the pan with waxed paper and spray the paper.
Sift cake flour, 1/2 cup superfine sugar, and salt into a bowl. Sift the mixture two more times.
Beat egg whites in a glass, metal, or ceramic bowl until foamy. Gradually add vanilla and cream of tartar and continue to beat until soft peaks form. Gradually beat in remaining 1/2 cup plus 2 tablespoons superfine sugar.
Gradually sift flour mixture over the egg white mixture, folding it in until just combined. Spread the batter evenly in the prepared pan.
Bake in the preheated oven until the top of the cake is lightly browned and springs back when lightly pressed, about 20 minutes.
Remove the cake and set it on a wire rack. Loosen the sides with a spatula and generously sift confectioners' sugar over the top. Cover the cake with a clean kitchen towel and invert onto a second wire rack. Remove the pan and peel off the waxed paper. Starting at the short end, roll up the cake and towel together. Place, seam-side down, on a rack and let cool completely, about 1 hour.
Simmer cranberries, sugar, and water in a pan over medium-low heat for 5 minutes. Strain well and return to the pan. Whisk in cornstarch and simmer until thick, about 2 minutes. Cover and chill until the cake has fully cooled.
Very gently unroll the cooled cake. Carefully spread the cranberry filling over the top, leaving a 1/2-inch border with no filling. Gently re-roll the cake and place, seam-side down, on a serving platter. Refrigerate for up to 2 hours before serving.