Separate the egg whites from the yolks of the eggs. Beat the egg whites with a pinch of salt to a thick snow. Beat the yolks with the sugar, vanilla and water.
Add the soft butter, beat well and add the flour. Pour in the milk, mix well, add the egg whites, while mixing very carefully.
Transfer the mixture to a buttered and floured cake form. Bake at 338°F (170 °C) for 45 min.
Once the cake is baked, open the door of the over and leave it to cool.
Turn over into a suitable plate and sprinkle with powdered sugar.