Clean the rhubarb and cut into 1 cm long pieces. With the juice, the vanilla sugar and, if necessary, additional sugar, sauté in a saucepan for 3 minutes, depending on your taste, and allow to drain a little. Dust with the pudding powder and spread on the bottom of an ovenproof dish.
For the crumble, mix the brown sugar, flour, oatmeal, oatmeal and cinnamon in a bowl. Knead in enough butter that crumbles of different sizes form and crumble onto the rhubarb. Bake at 180 ° C (top / bottom heat) for a good 30 minutes until golden brown and crispy.
Tastes lukewarm or, if you can`t wait, hot too, of course.
Tip: You can replace part of the rhubarb with other fruits, the combination with raspberries (350 g frozen raspberries) is very tasty. Serve either straight, with cream or ice cream.