Combine fruit, lemon juice, cinnamon, and pectin in a large sauce pan
Note: You may also add 1/2 teaspoon of butter to reduce foaming if desires. (I find this works best if you add the butter right away, rather than wait until the jam is already boiling)
Bring mixture to a full, rolling boil that can’t be stirred down.
Add sugar and stir until dissolved.
Allow mixture to come back to a full, rolling boil that cannot be stirred down, and allow to continue boiling for 1 minute.
Skim off any foam with a spoon.
Ladle jam into clean, hot jars, wipe rims clean, and fit with lids and rings.
Add jars to water bath canner, fitted with a canning rack.
Fill canner with hot water to 1-2 inches above jar tops
Bring to a boil, and process jars for 10 minutes
Allow canner to cool on its own for a few hours, or completely if possible before removing jars.
After jars are completely cool, check for sealing.
If the center of the lid springs back after pressing, the jar is not sealed. You can either store this jar in the fridge for a few weeks until it is used, or you can replace the lid with a new one, and process again.