Preheat oven to 400 degrees F.
Line a jelly roll pan or cookie sheet with parchment paper.
Sift the flour and cornstarch together. Stir to combine.
Separate the yolks from the whites. Place the egg whites and salt in a mixing bowl. Set the yolks aside in a medium bowl.
On medium-high speed, whip the whites until they are just beginning to thicken and hold their shape. Gradually add the sugar and the vanilla. Beat for a minute until batter forms a meringue. It will be glossy and stiff.
Whisk the yolks and the pumpkin puree until they are well blended. Scoop out 1/3 of the meringue. Combine with yolks. Whisk together until combined.
Add what you just mixed on top of the remaining meringue. Do not mix.
Add dry ingredients.
Using a large spatula, gently fold all the ingredients together. Fold until incorporated completely (especially the pumpkin), but do not over mix.
Scrape batter onto prepared baking sheet and spread evenly to make a large rectangle.
Bake for 8-10 minutes and is set to a light golden color. Do not let the finished cake sit for longer than a few minutes.
Spread out a clean kitchen towel. Lay down a piece of parchment paper. Dust parchment paper with powdered sugar.
Turn over the pan to let the cake fall onto the dusted towel. Peel away the parchment paper.
Lightly dust the cake with powdered sugar.
Lay a new parchment paper on top of cake.
Roll up the short side of the cake tightly in the kitchen towel and parchment paper. Tie another kitchen towel around the roll to secure. Then, let the cake cool to room temperature.
Prepare the filling.