Sterlise your jars and jam funnel if you are using one (see notes).
Place the chopped onion, vinegar, spices, sugar and salt in a heavy-bottomed pan and bring to the boil then simmer for a few minutes.
Add the rhubarb, reduce to a simmer and cook for 20-30 minutes until thickened.
Drag a wooden spoon through the chutney when you think it's ready. If it leaves a channel that doesn't immediately fill, it is ready.
Pop the funnel (if using one) into one jar at a time and fill with chutney, screwing on the lid tightly and leave to cool.
Store in a cool, dark cupboard for 3-4 months to mature.
Cook time does not include time to sterilise the jars.
There are two ways to sterilise jars before adding preserves like chutney.
THE TRADITIONAL METHOD - Wash the jars and lids in hot soapy water, then place on a tray in a hot oven for 15-20 minutes. Do not dry the jars and lids before placing them in the oven, just shake off the excess water.
THE MODERN METHOD - Run your jars and lids through a hot cycle in the dishwasher.
Pour the chutney into the jars while the chutney and jars are hot.Be careful not to put your finger inside the jar, lid or funnel (if using one) or you could introduce bacteria.Chutney can be stored unopened for up to a year (maybe even longer).Once open the chutney can be kept in the fridge and used for up to a month.