Wash and clean the rhubarb the day before and cut into small pieces. Sprinkle with 400g sugar and let it steep overnight.
Make a shortcrust pastry from 300g flour, 200g sugar, 200g butter and 1 egg and chill for 1 hour.
Put the rhubarb in a sieve, drain well, but catch the juice. Cook a pudding from 3/4 liter of the juice and the two pudding powders. Stir rhubarb into the pudding.
Line a springform pan with shortcrust pastry, pull up the edge nicely and add the rhubarb pudding mixture.