Mix with a blender 100 g of unsalted butter cut into cubes, 100 g of sugar and 1 spoon of vanilla extract. Mix until no lumps

3 eggs, separate the egg white from the yolk. The egg white goes in the refrigerator, the yolk in the mix, mix well.

Add 150g of white flour and mix well

Add 50 g of potato starch and mix well

Add 2 small bags of baking powder and mix well. Dough becomes serious and real. This is happenings

Butter the baking tray well, add dough evenly, have some edges on the side

Add cut rhubarb on the dough

Put in the oven, 180’, fan, middle of oven, no trays. For 50 minutes

10’ before the 50’ are through, mix in a bowl 100 g of sugar with the 3 egg whites. Mix well high speed to “soft peaks”

When 50’ are oven, take the tray out, spread the soft peaks on the dough. 150’ for 15’ and you’re done.