- To make peach salsa, heat gas or adjust charcoal grill to high. Brush peach halves and onion with 2 tablespoons olive oil. Set on grill and cook until slightly charred on all sides.
- Transfer to cutting board and let cool. Quarter and mince each, then transfer to a small non-reactive bowl. Stir in lime juice, hot pepper, remaining 2 tablespoons oil, and cilantro. Season to taste with salt.
- For pork, thoroughly season tenderloin. Place on grill over medium-high heat; let cook 2-3 minutes. Using tongs, quarter-turn pork, leaving same side facing down; let cook 2-3 minutes. Turn pork over with tongs and repeat above steps. Cook until meat reaches internal temperature of 140-145 degrees on meat thermometer.
Let rest 10 minutes. Thinly slice meat against the grain and top with grilled peach salsa.