Combine the blueberries and sugar in a medium saucepan and stir with a spoon to incorporate. Bring to a boil, reduce the heat to medium, and simmer for about 5 minutes.

Whisk together water, lemon juice and cornstarch in a small bowl to create a slurry. Turn the heat back up on blueberry mixture until it comes to a boil, add the slurry mixture and stir until jam has thickened about 2 – 3 minutes. The jam should coat the back of a spoon.

Allow to cool to room temperature before serving. Store in an airtight container for up to 10 days.