makes 3 cups
1 cup lemon juice
1 cup water
1 cup white sugar
1 tablespoon lemon zest
1 tablespoon cornstarch
3 half pint canning jars with lids and rings
Heat lemon juice, water, sugar, lemon zest, and cornstarch in a pot over medium heat. Simmer until thickened, about 5 minutes; remove from heat.
Sterilize the jars and lids in boiling water for at least 5 minutes.
Pour the lemon syrup into the hot, sterilized jars, filling the jars to within 1/4 inch of the top.
Run a knife or a thin spatula around the insides of the jars after they have been filled to remove any air bubbles.
Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with lids, and screw on rings.
Process jars in boiling water in a large pot for 10 minutes; remove jars from pot and allow to cool.
Once cool, press the top of each lid with a finger, ensuring that the seal is tight.