For the rhubarb cake, beat egg whites until firm. Mix egg yolks, oil, water and sugar. Add flour, baking powder and vanilla sugar and finally fold in the snow.
Sprinkle a cinnamon sugar mixture into the dough for refinement. Pour the batter onto a baking sheet lined with parchment paper and then spread the washed, peeled and chopped rhubarb on top.
Sprinkle the rhubarb cake with a light mixture of cinnamon sugar and give in the preheated oven for about 25-30 minutes at 190 degrees.