Prepare rhubarb: Discard the leaves, they are poisonous. Wash, dry and roughly chop the stalks. Place them in a food processor.
Prepare oranges: Remove the thick orange peel and the outer white thin peel with a small knife. Remove all the pits. Chop roughly and place in the food processor.
Process until smooth.
Sterilize jars: Do it before starting to cook the marmalade. Place upside down on clean kitchen towels.
Prepare pectin: Place pectin and 1 heaped tablespoon of the sugar in a small bowl. Mix well and set aside until needed.
Cook: Pour the rhubarb-orange mixture into a large pot. Bring to a boil while stirring often. Once it comes to a rolling boil, set the timer to 3 minutes. Cook, stirring continuously. After 3 minutes, whisk in the pectin-sugar mixture. Make sure you stir well so that the pectin doesn’t clump. Boil for another minute while stirring continuously.
Transfer the jam to the jars. Using a jam funnel makes things easier (Amazon affiliate link).
Can: In a canner for 5 minutes if the jars are sterilized and for 10 minutes if they are not. Once the time is up, let the jars in the canner for 5 more minutes. Remove carefully with a jar lifter. Read the blog post for more information on canning (Amazon affiliate link).
Cool: Let cool completely, undisturbed, on clean towels. Check if the jars are sealed. Any jars that are not sealed should be kept in the fridge and consumed within 2 weeks or so.
Weighed after removing the thick peel and the outer layer of white peel. Don’t remove the white peel between the fillets, unless you want no bitter notes in the jam.
You can replace one orange with one grapefruit, it adds more bitter notes.
Always use pectin according to the packet’s instructions. If the instructions regarding the needed amount of pectin, the way of using it, or the cooking times differ from mine, make sure you follow the instructions on the packet.