For the Powidl bring the plums with very little water to a boil, reduce heat.
Slowly boil down the plums until thick (takes about 6-8 hours) while stirring well again and again.
When it reaches the right consistency, add rum and cinnamon. Pour into clean screw-top jars and seal the Powidl immediately.
Preparation Tip:
If you like it sweeter you can also add some sugar to the powidl.