Add blueberries, maple syrup and lemon juice to a medium saucepan and stir to combine.
Heat over medium heat and bring to a gentle boil, then reduce heat to low.
In a small bowl, combine 2 tablespoons of water and 1 tablespoon cornstarch to make a slurry. Stir until smooth, then gently fold into the pan with the blueberries, taking care not to crush them.
Cook, uncovered, for 5-10 minutes until the mixture is reduced and thickened. (It should coat the back of a spoon).
Remove from heat and add vanilla extract, lemon zest and a pinch of salt.
Allow to cool before serving.
