Cherry Note: Dark sweet cherries are a type of cherry that is often sold frozen. Despite the name, they don't contain any added sweeteners. A 12-ounce bag will provide close to 2½ cups of frozen cherries, and a 16-ounce bag will provide a little over 3 cups. If you opt to use other cherries, you might need to adjust the sweetener and lemon juice, to taste. And if you use fresh cherries, you might need to adjust the chia see amount, too.
Chia Note: You can easily adjust the thickness of this jam. Simply add more chia seeds if it doesn't set up enough. They will absorb moisture even if the mixture is chilled. But if you add a few too many chia seeds and it sets up too much, just add a splash of juice or water.