Cut the rhubarb into 3 cm pieces. Cut the apples into 4 pieces, remove the seeds. Cut each quarter into medium cubes.
Bring to a boil 2.5-3 liters. drinking water. Put in the rhubarb, apples, sugar, vanilla seeds and cinnamon stick. Bring back to a boil.
During this time, peel a thin (yellow only) layer of zest with a vegetable peeler. Add to saucepan and remove compote from heat. Leave it to infuse for 6-8 hours. Before serving, if necessary, strain and refrigerate.