This classic recipe is a great way to use up very ripe plums that are about to go bad.
Feel free to increase or decrease the amount of sugar in this jam depending on your sweet tooth.
Rinse and halve the plums. Remove the stones and thinly slice. Mix with the lemon zest, lemon juice, cinnamon, vanilla seeds, and sugar. Set aside for 2 hours, then transfer to a pot, bring to a boil, and cook for 4 minutes.
Remove the spices, and divide the jam into prepared glasses. Seal tightly, and let cool completely.