Preheat oven to 350 degrees F. Wash cherries and lay them out on a baking sheet lined with parchment paper (for easier clean up). Drizzle the cherries with a tiny bit of olive oil and sprinkle with salt.
Roast cherries for 15-20 minutes until they are slightly charred and bursting. Remove and let the cherries cool and then pop out the seeds. You should be able to just push them out with your fingers.
Add pitted cherries to a food processor with vinegar, a pinch of sugar and mustard, and salt and pepper. Pulse a few times to combine. Then drizzle in olive oil and pulse until smooth.
Taste and adjust seasoning to your liking. Store in the fridge for 2 weeks!