Step 1

Rinse the blueberries thoroughly and remove any stems or leaves. If using frozen blueberries, ensure they are fully thawed.

Step 2

Combine the cornstarch, sugar, and salt in a small saucepan. Whisk in the water and stir until mostly dissolved.

Step 3

Add the blueberries, lemon zest, and lemon juice, and place the saucepan over medium heat.

Step 4

Let the sauce simmer, stirring frequently, until it thickens.

Step 5

Remove the saucepan from the heat and pour the sauce into a heatproof bowl to cool. It will thicken more as it cools.

Step 6

Serve the blueberry sauce warm or chilled.