Melt butter slowly, let it cool for a couple of minutes and mix with white sugar. Pre-heat oven to 180C.

Wash the orange, grate the peel, make the juice and add go ghe butter and sugar mix. Add the yolks and mix until everything is well integrated.

Sift the flour and add. Add also the baking powder, the salt and the milk.

Beat the whites to hard peaks and add to the mass. Mix until fhey are fully ingegrated.in slow movements.

Grease the mold with butter, cover with a thin layer of flour, pour the mass and sprinkle some vanilla sugar on top. Cook for 25-30 minutes or until the knife comes out clean.