Cut the rhubarbs in small pieces, put them in a cooking pan and add a little bit of water (don't cover them).
Cook the rhubarb until soft. Depending on your preference you can use a hand blender to make a smooth mass, or keep it a bit more chunky.
Then add the marrow of the vanilla pod as well as the sugar. I like it when my confiture isn't too sweet, but if you like full sweet confiture, you can use 150 gr of jelly sugar in 150 gr of rhubarb.
Cook for a few more minutes and then put the confiture in a sterilized jar to let it cool off before use.