Rinse tomatoes and pat dry. Eliminate their stems, cut them into quarters and empty them of their juice, their pips and the white part of the heart.
In a glass or stainless steel terrine, mix the tomato quarters, sugar and lemon juice. Place a sheet of parchment paper on top (to prevent the fruit from oxidizing) and leave to macerate for at least 12 hours.
Then pour the mixture into a jam bowl. add the cinnamon stick. Boil for 10 minutes, stirring occasionally. When the tomato wedges are tender, remove the cinnamon stick. Pass everything through a vegetable mill (fine grid). Pour back into the basin. Keep cooking over low heat, stirring continuously for 10 minutes.
Scum carefully. Check that the jam coats. Pour it into jars immediately. Add cinnamon chips in each and cover. Wait at least 10 days before serving.
Note:I personally turn the jars upside down after potting, and let them cool like this. This allows some sterilization.