Peel orange peel thinly and chop finely. Fillet the fruit flesh and cut into small cubes.
Place the rhubarb with the water in a heavy saucepan and soften for about 15 min at a low temperature with the lid closed.
Drain off about 2 dl of liquid (based on 1 kg of rhubarb). Blend the rhubarb briefly in a hand blender. Return to the saucepan with the orange cubes and zest, rum, vanilla pod and sugar and cook for about 15 minutes.
Remove from the heat. Remove the vanilla pod, fill the jam into preheated jars and seal them on the spot.
According to Oskar Marti, Ein Poet am Küchenherd, Frühling in der Hallwag, Küche, Bern,