Remove the eggs from the refrigerator about an hour before preparing the sponge.
Preheat oven to 350 degrees F and line a 10 x 15 inch baking sheet with parchment paper.
Separate the eggs, place the whites in a bowl and set aside. Add the yolks to a large bowl and whisk vigorously with sugar until pale and frothy, about 3 minutes. A hand held mixer or egg beater may be used for this step. Stir in vanilla.
Sift flour, baking powder and salt and use a rubber spatula to stir into the egg mixture until smooth. At this point the batter will be quite thick and have a pasty texture.
Whisk the egg whites until stiff peaks form. Fold half the egg whites into the batter. Stir in the remaining egg whites just until there are no visible white streaks of egg whites.
Pour the mixture onto the prepared baking sheet and spread evenly with a spatula. Tap the baking sheet a few times on your counter to remove air bubbles in the batter.
Bake for 10-12 minutes until golden and spongy. Do not overbake the sponge.
While the cake is baking, tear off a sheet of parchment paper the same size as the baking sheet. Dust the entire surface with powdered sugar. A clean dish towel may be used in place of the parchment paper.
When the cake is out of the oven, immediately invert it onto the prepared sheet of parchment paper. Roll, using the parchment paper to guide you, from the short end. Wrap in the parchment paper and let cool completely.