Watermelon Jam

Quarter the watermelon. Remove the rind and the seeds. Then dice and let drain in a sieve for 30 minutes. Weigh the melon cubes. You need 750 grams sugar for each 1000 grams of melon. Mix the melon cubes with the sugar and let it rest for 1 hour. Put into a pot together with lemon juice, vanilla bean and lemon peel. Cook for 1 to 1 1/2 hours at low heat, stir frequently. Start testing after 1 hour if it jells already. Remove the vanilla bean, pour everything in clean jars and seal.