In a small saucepan, whisk together water, lemon juice, sugar, and cornstarch until smooth.

Add the cherries to the saucepan and stir to coat.

Place the saucepan over medium heat and bring the mixture to a simmer, stirring frequently.

Continue to cook for 5 to 7 minutes until the liquid thickens and turns translucent and the cherries soften slightly.

Remove from heat and stir in the vanilla extract.

Allow to cool slightly before serving; the sauce will continue to thicken as it cools.