Mix together the eggs with salt and sugar, then start whipping. The volume needs to increase and the mass should become white. In the classic sponge cake recipe baking powder isn't used, so if the eggs are whipped well enough then the cake will turn out very fluffy.
Combine the flour with cornstarch and vanilla and sift into the mixed eggs.
Carefully mix together. Don't overmix. If you do, the dough will lose the air bubbles.
Pour into the mold and send to the preheated oven (170°C) for 20-25 minutes. Don't open the oven while the cake is baking!
You can use a wooden stick to check when it's done - the stick should be dry and clean, this means the cake is ready. Leave the sponge cake to cool down. It may settle down a bit, but it's absolutely normal - don't worry!