Place the cherries and the syrup or water in a small saucepan along with the sugar, butter and lemon juice. Bring to a boil. If using fresh or frozen cherries, reduce the heat and simmer for another 3 minutes. Stir in the cornstarch mixture, stirring continually until the sauce is thickened, about 1 minute. Remove from heat and stir in the almond extract.
Cover and store in the fridge where it will keep for up to a week.