ready in 1 hr 44 min.
Put the cherries in a large saucepan and add the zest, cinnamon and sugar. Cover and leave to macerate for at least 1 hour.
Bring to the boil, stirring, and cook at a rolling boil for around 4 minutes. Test that it will set. Remove the cinnamon and lemon zest and roughly purée the jam.
Transfer immediately to clean jam jars, seal and leave to cool.