1
Make the sponge cake:
Preheat oven to 355ºF/180ºC.
Grease a 7.85 inch/20 cm diameter removable pan with butter, sprinkle with flour and turn to remove the excess. Set aside.
Sift the flour, set aside. In the bowl of the KitchenAid or a stand mixer, add the eggs along with the sugar and salt. Beat, increasing progressively the speed without reaching the maximum, until reaching the rippon stage* (see in NOTES).
Add the flour little by little as we integrate with enveloping movements helping us with a spatula. Incorporate the butter and integrate again with enveloping and soft movements.
Pour the mixture into the pan, tap gently to settle the batter and place in the oven. Bake for 30 minutes or until a toothpick in the center comes out clean. Remove from the oven, let it rest for 15 minutes and unmold. Let it cool completely on a rack. Once it has cooled completely, wrap with film and refrigerate until the next day.