Cherry Chutney

Pit the cherries and cut them in half. Discard the pits.
Place the mustard seeds and cumin seeds in a dry saucepan over medium heat. Toast for 1 to 2 minutes, stirring frequently, until fragrant. Remove from the heat and let cool slightly. Grind the toasted mustard seeds and cumin seeds into a coarse powder using a spice grinder or mortar and pestle.
Add the cherries, onion, sugar, apple cider vinegar, ginger, garlic, ground mustard-cumin mixture, cinnamon stick, crushed red pepper flakes, and salt to a medium saucepan. Stir to combine.
Place the saucepan over medium heat and bring the mixture to a gentle simmer.
Cook uncovered for 30-35 minutes, stirring occasionally, until the cherries soften and the mixture thickens into a glossy, spoonable chutney.
As the cherries cook, use the back of a spoon to lightly mash some of the fruit while leaving plenty of larger pieces for texture.
Remove the cinnamon stick and taste. Add a little extra sugar or vinegar if needed to balance the flavors.
Allow the chutney to cool for 15 to 20 minutes. It will continue to thicken as it cools. Transfer to a clean glass jar and refrigerate until ready to use.