Place peaches and lemon zest and juice. Bring to a simmer; cook 10-15 minutes or until peaches start to soften, stirring occasionally.
Stir in sugar, cinnamon (if using) and salt; cook another 10-15 minutes or until jam has mostly thickened (a little liquid is okay), stirring occasionally.
Remove from heat; let sit 15-20 minutes or until mostly cooled.
Transfer mixture to a high-speed blender. Blend on the lowest setting until jam reaches desired texture (I like it slightly chunky, but pureed enough so there aren’t pieces of peel). Alternatively, blend in the pot using an immersion blender. Taste and adjust seasoning, if necessary.
Transfer to jars without lids; let completely cool. Secure lids on the jars; refrigerate up to 1 week.