For the dough, put all the ingredients except for the rhubarb in a bowl and mix with the mixer on the highest setting until the dough is nice and smooth (approx. 2 minutes). Then place on a high baking sheet (drip pan) and spread the peeled rhubarb, cut into pieces approx. 2 cm in size. Possibly press the rhubarb pieces lightly.
For the crumble, knead the softened butter in small pieces with the flour, sugar and vanilla sugar to form crumbs. This is best done by hand. Sprinkle the cake with the crumble. Bake at 160 ° C (fan oven) for approx. 45 minutes.
The cake is very juicy and will keep juicy for the next few days. So if you don`t want to eat it on the same day, you can replace 1/2 glass of flour with cornstarch. This binds the moisture in the rhubarb.
The cake is also suitable for other fruit such as B. Apples. It should be densely packed as it rises well.