Wash, peel and cut the rhubarb into small pieces. Halve the vanilla pod lengthways and scrape out the pulp.
In a large bowl, mix the eggs with the sugar, a pinch of salt, the milk, the oil and the vanilla pulp. Mix the flour with the baking powder, sift over the egg mixture and fold in loosely with a large wooden spoon, do not (!) Mix with the mixer.
For the crumble, knead the flour, sugar, 1 pinch of salt and butter to make crumble. Do not knead for too long.
Spread the batter in muffin paper cases. Spread the rhubarb pieces on top and press down a little. Sprinkle the crumble on top and bake the muffins in a preheated oven at 180 ° C for 20-25 minutes until golden brown.