Place rhubarb into TM bowl and blend 30 sec/speed 8.
Place the pulp into a nutmilk bag and squeeze out the juice, reserving all of it. You will need 300g juice for this recipe. You can use the rest in drinks, smoothies etc.
Discard the solids.
Place sugar and lemon zest into a clean dry TM bowl and mill 10 sec/speed 10.
Add butter and chop 6 sec/speed 6.
Add all remaining ingredients including rhubarb juice and cook 10 min/80°C/speed 5.
Cook 4 min/90°C/speed 5. Pour into hot sterlised jars and seal. This will keep up to 4 weeks in the fridge unopened. Once opened, use as quickly as possible...not that I think I need to tell you that!