Preheat the oven to 350 F (180 C). Line two baking sheets with parchment paper. Prepare a pastry bag fitted with a round 1/2-inch (1cm) tip.
Beat the egg yolks with half of sugar (about 2 tablespoons - 30g), salt and vanilla extract until creamy, thick and light yellow.
In another bowl beat the egg whites with salt until foamy. Gradually add the rest of the sugar and continue whipping until stiff peaks form.
Fold a part of the egg whites into the egg yolk mixture then fold everything into the remaining egg whites.
Sift the flour over the egg mixture. With a rubber spatula gently fold it in until smooth and well combined.
Transfer half of the batter to the prepared piping bag. Pipe the batter into 4 inches(10 cm) lines, keeping distance between them. Repeat with the rest of the batter.
Dust the cookies lightly with powdered sugar. Let them rest for about 5 minutes and dust the tops again with powdered sugar.
Bake for about 13-15 minutes or until golden brown.
Remove and transfer the ladyfingers to a cooling rack. Serve immediately or store in an airtight container for a couple of days.