1Stem and pit cherries, reserving the pits. Place pits in a resealable plastic bag, cover the bag with a kitchen towel, and, using a meat mallet or the bottom of a frying pan, smash the pits.
2Place sugar, water, vanilla bean pod and seeds, and smashed cherry pits in a small saucepan over medium heat, stirring occasionally, until the mixture comes to a boil. Remove from heat and let cool to room temperature, about 40 minutes.
3Place a fine-mesh strainer over a medium container with a spout and strain the syrup. Reserve the vanilla bean pod, making sure to remove any trace of the pits, and discard the remaining solids. Add the maraschino liqueur to the syrup and stir to combine.
4Place cherries in a 1-quart container with a tightfitting lid and tuck the vanilla bean pod in the center. Pour the maraschino syrup over the cherries, cover tightly, and refrigerate for at least 5 days before serving. Store in the refrigerator for up to 3 weeks.