Step 1

Boil the jars and lids, or rinse them with very hot water.

Step 2

Wash the rhubarb and remove leaves, then cut into small pieces; weigh afterwards.

Step 3

Slice the vanilla pod open lengthwise with a sharp knife and scrape out the seeds. Add both the seeds and pod below.

Step 4

Mix the cardamom, rhubarb, vanilla pod, apple juice and gelling sugar in a large saucepan or pot.

Step 5

Bring everything to a boil while stirring. Simmer for at least 3 minutes, stirring constantly.

Step 6

Remove the vanilla pod.

Step 7

Perform a gel test: put 1-2 teaspoons of the hot fruit mixture on a plate that has been chilled in the fridge. If the gelation sample does not set, simply continue to boil for 1 minute. Or, stir in 1 tablespoon of citrus juice or vinegar.

Step 8

Skim the foam off the top if necessary. Fill the prepared jars immediately to the brim.

Step 9

Close the jars with the lids and turn them upside down immediately. Leave them standing on the lids for about 5 minutes.