Combine all ingredients in a large pot (I use a 4qt Dutch oven). Leave for 1-2 hours at room temperature until the rhubarb releases its juices.

Bring the mixture to a boil over medium heat and cook for around 25 minutes, stirring occasionally until the mixture thickens. To check for doneness, coat a spoon with the jam and quickly trace a line across the back of it with your fingertip. If the line remains clear, the jam is ready. You can also place a plate in the freezer while the jam is cooking. Once done, spoon some jam on it and tilt it. If the jam runs down slowly, it’s done.

Pour the hot jam into sterile jars and close them tightly. Refrigerate overnight before serving. This jam is also great for water bath canning if you want to store it for a longer time.