1. Heat a skillet over medium-high heat. Coat pan with cooking spray. Sprinkle pork with 1/4 teaspoon salt and black pepper. Add pork to pan; cook 16 minutes or until a thermometer registers 145°, turning to brown on all sides. Remove pork; let stand for 10 minutes.
2. Combine red onion and the next 6 ingredients (through serrano pepper); toss. Sprinkle mixture with remaining 1/4 teaspoon salt and mint; toss. Slice pork crosswise; serve with mango salsa.