Pit the cherries and slice in half.
Add all ingredients to a saucepan and bring to a boil, then reduce the heat to a simmer (low heat) and let cook for 30 minutes.
Remove from the heat and use a wooden spoon or similar to crush the cherries in the pot, really getting as much juice out as possible!
Pour the contents of the saucepan into a sieve (sitting above a wide bowl). Then pour the liquid into a jar and the cherries in a separate container.