Preheat your oven to 400ºF with the oven rack in the center. Line a sheet pan (13x18") with parchment paper.
Fill your saucepan with 2-3" water and bring to a boil over medium high heat until boiling then reduce heat to medium or until water is simmering
Place eggs, sugar and salt into the mixing bowl and blend together with a whisk
Place the bowl with mixture on top of your simmering water. Using your whisk, stir the egg mixture slowly until the sugar granules dissolve (about 110ºF) Remove from the heat.
Attach your bowl to your stand mixer with the whisk attachment. Add in your vanilla and whisk on high for 5-7 minutes until you reach the ribbon stage (see notes). The mixture should triple in volume and lighten in color.
Sift in ⅓ of your flour mixture and fold (see notes) the flour in gently without damaging the structure of your egg mixture. Repeat two more times with the flour until just combined.
Spread batter evenly into your prepared sheet pan and spread with an offset spatula or knife all the way to the edges of the pan. Do not grease your pan.
Bake for 8 minutes and then remove from the oven and place onto a cooling rack
Immediately use a paring knife to carefully cut the edge of the sponge away from the sides of the pan. Dust the surface with powdered sugar. Place another piece of parchment on top of the cake, then another cooling rack and flip over to release the cake from the pan.
Remove the parchment paper carefully and dust the surface with more powdered sugar.
Place a tea towel over the top of the cake and carefully roll into a spiral. Place into the fridge to cool for one hour before filling with frosting.