Pour half the blueberries (1 cup) into a medium saucepan and set aside the remaining 1 cup. Add the water, honey, and cinnamon and cook over medium-high heat.
Once boiling, reduce to a simmer and cook for an additional 10 minutes. After 10 minutes, gently smash the blueberries against the pan using a wooden or plastic spatula.
Add the remaining blueberries and cook for an additional 5-6 minutes to heat through. Add lemon juice, if desired, to taste. (This will make the blueberry flavor pop a little bit more but isn't necessary.)
Traditionally served warm, but can serve cold as well. Store in refrigerator in a mason jar for up to a week.