Pat pork dry with paper towels. Season with salt and black pepper. Combine brown sugar, paprika, cumin, garlic powder, and cayenne pepper in a bowl. Coat chops evenly on all sides with spice mixture. Cover and chill 3 hours.
Set up grill for direct cooking and heat to medium-high. Once hot, clean and lightly oil grates.
Grill pork, turning occasionally, until charred and internal temperature registers 145°F on an instant read thermometer, 8 to 10 minutes. Let stand 5 minutes before serving with Peach Relish.