1. Wash rhubarb, clean and cut in 3 cm long pieces. Weigh out 1.6 kg cleaned rhubarb; boil with 600 ml water and then let simmer for 10 minutes, until the fruit pulp dissolves. Place the fruit pulp in a cheesecloth and let drip completely through a sieve into a bowl. Afterwards carefully press out the cheesecloth and let the juice cool. Be careful to make sure that no pulp gets into the juice.
2. Take 900 ml of the juice and stir with jelly sugar and lemon juice in a large pan and very slowly bring to a boil. Once boiling rapidly, let boil for three minutes and stir constantly.
3. Cut open vanilla pod and add to pan. To sample the jelly, take some and place it on a small plate and let cool in the refrigerator. As soon as this solidifies, the jelly is also done. Otherwise let it cook a little longer. Use a slotted spoon to skim the foam.
4. Fill clean screw-top jars to the rim with the finished jelly. Screw the jars tight and let stand on head for five minutes so that the cover is sterilized as well.