Cut rhubarb into 3 cm long pieces. Cut the apples into 4 pieces and remove the seeds. Slice each quarter with medium cubes. Bring 2.5-3 liters drinking water to the boil. Put there rhubarb, apples, sugar, vanilla seeds and a cinnamon stick. Bring to the boil once again. Meanwhile, remove the thin (only yellow) layer of a lemon peel with a peeler. Add to the pan and remove the kompot from fire. Let it stand for 6-8 hours. Strain and cool before feeding, if necessary.