Make shortcrust pastry, chill, line the springform pan, pull up the edge approx. 2 cm.
Wash the rhubarb, do not peel, dice.
Spread a thin layer of oil on the shortcrust pastry base, place the rhubarb on top and bake for 20 minutes at 160 °.
In the meantime, make the icing: whip the egg white until stiff, slowly beat in 100 g sugar until it becomes stiff.
Whisk the egg yolk, vanilla sugar and cornstarch with the cream and stir gently into the mixture.
Take the rhubarb cake out of the oven, sprinkle with 50 g of sugar and distribute the icing evenly on top. Bake for another 10 minutes until light brown.
Let the cake cool down for 1/2 hour, only then carefully remove it from the tin.