This sauce is part of our recipe for Pineapple Upside Down Mini-Cakes.
Combine 1 cup water, sugar, vanilla bean and seeds, cinnamon stick, and salt over high heat. Stir to dissolve sugar and boil for 2 minutes.
Add 2 cups cherries and simmer until syrup is thick and reduced by a little more than half, about 25 minutes. Strain cherries (reserve for another use), pressing on solids to release as much liquid as possible. Add liquid to pan along with remaining 3 cups cherries and return to a boil. Remove cinnamon stick and vanilla bean, cool to room temperature, and chill in refrigerator until cold, about 1 hour.