• Wash the plums, slice them in half, and remove the pits.
• Transfer the plums to your slow cooker and add the water. Place the lid on the slow cooker and cook for 2 hours on high, or until the plums are soft and have released their liquid.
• Using an immersion blender, blend the plums until they are pureed.
• Add the sugar, cinnamon, and lemon juice and stir well.
• Lay a wooden spoon across the rim of the slow cooker and set the lid back on so it vents.
• Turn the slow cooker down to low and cook the plums for 6 to 10 hours until it’s nice and thick. Adjust the sweetness to taste.
• Ladle into containers and store in the fridge, or process as below for long-term storage.

To Can:

• Ladle the plum butter into half-pint jars, leaving 1/4 inch of headspace.
• Wipe the rims of the jars with a damp paper towel or kitchen towel, then place the lids and rings on finger-tight.
• Process in a water bath canner for 10 minutes, adjusting the time for your altitude.
• When the time’s up, turn off the canner and let it sit for 5 minutes, then remove the jars and set them on a towel. Leave them undisturbed for 12 to 24 hours to let the seals set. Any jars that don’t seal should be reprocessed with a new lid or placed in the fridge.

To Freeze:

• Let the plum butter cool, then ladle into freezer-safe containers, leaving 1 inch of room for expansion.
• Label and place in the freezer.