Mix all the ingredients, except the flour, with an electric mixer, trying to introduce as little air as possible. (1)
Add the flour and continue beating until a smooth, lump-free mixture is obtained.
Strain the mixture through a sieve to remove any excess air that may remain.
Cover a baking pan with baking paper, previously wrinkled and moistened, then pour the mixture into the pan. (2)
Bake at 200 ºC for 20 minutes, then bake for 5 more minutes at 220 ºC.
Allow to cool before serving.