Preheat oven to 180°C (350°F). Line a 12" by 18" cookie sheet with parchment paper.
Beat the eggs: Crack the eggs into a clean bowl of a stand mixer. Add the salt and mix on high speed with the whisk attachment. After about 30 seconds, gradually pour the sugar into the stand mixer while it is running. The eggs will increase in volume considerably and get very foamy. This may take 6-8 minutes. You will know it is ready when you lift the whisk out of the egg mixture and can make a figure eight from the ribbon falling off the whisk onto the rest of the batter. The figure eight should sit on top of the batter for about 10 seconds before melting back into the batter. If it dissolves faster than 10 seconds, beat the eggs some more. Add vanilla extract.
6 large eggs, ¼ tsp salt, 1 cup sugar, 1 tsp pure vanilla extract
Fold in the flour: Sift the flour and baking powder into the bowl with the beaten eggs. Using a spatula, carefully fold the flour into the egg mixture. Be gentle so as not to deflate the eggs. Stop folding as soon as you stop seeing streaks of flour in the batter.
1 cup flour, ½ tsp baking powder
Bake: Smooth the batter onto the lined baking sheet. Bake in middle of oven for 18-20 minutes, checking for doneness at 18 minutes. It is ready once a toothpick inserted in the center comes out clean and it springs back a little when you press onto the surface of the sponge.
Remove from oven and let cool for 1 minute. Flip over onto a cooling rack to remove the parchment paper on the back. Peel off the parchment paper and flip back over so the top surface of the cake is on top again.
Roll: Immediately start rolling the sponge by rolling the short end of the roll onto itself. Let the roll cool on the cooling rack. You want to roll the sponge as soon as possible so that it doesn't crack.