Half peaches and remove pits. Drizzle the peaches, onion, and chiles with olive oil and sprinkle with salt. Place on a pre-heated, well oiled grill and grill for 8 to 10 minutes, turning halfway through. Remove from grill and allow to cool for a few minutes before handling. Remove any loose skin from the chiles as well as the seeds and stems and place in a food processor with the onion and cilantro. Purée until well minced before adding the peaches. Rough chop the peaches then add them to the food processor with lime juice and pulse until incorporated but still a little chunky. Check for seasonings then add more salt or lime juice if needed.