Bring the cherries and sugar to a rolling boil over high heat.

Use a potato masher to crush the fruit as it's cooking.

If any scum forms, skim it off with a spoon.

When the liquid begins to thicken add the lemon juice and balsamic vinegar.

Continue to cook for a few minutes more. Make sure to stir frequently.

You'll notice the jam will become really shiny and it will cling to the spoon instead of pouring off.

Remove the plate from the freezer and transfer a small amount of the liquid to the plate.

Return the plate to the freezer and after a few minutes pull your finger through the puddle of jam. You should see a path on the plate and what's on your finger should resemble jam.

Transfer the jam to clean, heat proof jars. If freezing, make sure to leave plenty of head space.

Store the jam in the fridge for several months, longer if freezing.