Separate the eggs, beat the yolks with the sugar, vanilla sugar and lemon juice until frothy. Beat the egg whites until stiff and fold into the egg yolk mixture.
Heat the fat in a pan, add the dough and smooth it out. Bake with the lid closed on the lowest setting for 15 to 20 minutes.
If the omelette is done on top (it should not be turned), slide it onto a plate and fill it with fruit, jam or chocolate to taste and sprinkle with powdered sugar.