Rinse the lemon, then zest it using a zester grater or small cheese grater. Set the zest aside in a small bowl.
Cut the lemon in half, then squeeze the juice into a small bowl. Set aside.
Rinse the blueberries, and add them to a medium saucepan with 1 cup of water. Smash the berries as much as possible using a potato masher or pastry blender.
Bring the berries to a boil over high heat. Then, reduce the heat to medium-low and set a timer for 15 minutes.
Once the berries have simmered for a while, give them a quick stir and mash any remaining whole blueberries. Using a fine mesh strainer (and bowl underneath), strain out the blueberry skins and stems. I used the back of a spoon to get as much liquid out as possible.
Pour the syrup back into the saucepan. Add in the lemon zest and granulated sugar, then stir to combine. Bring this mixture to a boil, then let it simmer over medium-low heat for 10 minutes.
Add the lemon juice to the saucepan and bring to a boil once more. Let this boil for about 2 minutes.
Let the syrup cool completely before serving. Enjoy!