Remove the skins, stems and seeds from the persimmons and cut into small pieces.
Combine the diced persimmon with the sugar, lemon slices and vanilla bean pod in a mixing bowl and mix well to dissolve the sugar with the persimmon pulp.
Transfer the fruit mixture into a cooking pan and bring to the boil. Stir constantly and skim off impurities.
Lower the heat and simmer to reduce for another 20-25 minutes. Evaluate the texture of the jam.
When ready, remove from the heat and discard the lemon slices and vanilla bean pod. You can stop here if you want, but for a smoother consistency, use an immersion blender to blend the chunks to a finer consistency. Pour the hot jam into clean sterilized, airtight jars.
You can store the jam for up to a year in your pantry if unopened. Once opened, it lasts up to a month in the fridge.