Put lemon pith and pips in a muslin cloth bag and place it in a big pan along with the rhubarb pulp and q bit of water

Stir until the rhubarb soft. This will help release some pectin of the lemon.

Add some shop bought or home made pectin. A cheese should have a hard consistency but rhubarb doesn't contain much pectin

Simmer until set. it's ready when you can form a channel along the bottom of the pan when you run the spoon along.

Pot into warm sterilised jars and seal.