Put the blueberries in a tall stainless steel or enamel lined pot, cover, and turn the heat to medium. Gently stir the berries occasionally.

Bring the pot to a gentle simmer, stirring occasionally, then turn the heat off, cover, and cool for 20 minutes. Remove the lid and strain the berries in a strainer without pressing on them. Reserve the cooked berries for making blueberry fruit leather.

Take the blueberry juice put it into a smaller pot, make a note of how much juice there is, then reduce it at a brisk simmer until only 30% of the original volume remains.

Turn the heat off, add the sugar and lemon juice, pour it piping hot into a pint jar, screw on the lid, turn it upside down, and allow to cool.

The juice reduction will keep at room temperature as long as it’s sealed. After sealing, refrigerate it.