How to Make It
Heat a grill pan over medium-high. Sprinkle pork evenly with salt and black pepper. Add to grill pan; cook, turning occasionally, until a thermometer inserted in thickest portion of meat registers 135°F, 10 to 12 minutes. Transfer pork to a cutting board; let rest 5 minutes.
Meanwhile, cut jalapeño in half crosswise. (If desired, remove and discard seeds.) Finely chop 1 jalapeño half. Thinly slice remaining half crosswise into rounds. Place chopped jalapeño, peaches, mint jelly, vinegar, and brown sugar in a small saucepan; cook over medium-high, stirring occasionally, until thick and syrupy, about 4 minutes.
Cut pork into ½-inch-thick slices; arrange on a platter. Spoon peach mixture over pork. Sprinkle with sliced jalapeño rounds; garnish with cilantro.