1. Combine pork and 1 tablespoon juice; let stand 10 minutes. Heat a grill pan over medium-high heat. Coat pan with cooking spray. Add pineapple and onion; cook 4 minutes on each side or until onion is tender. Coarsely chop pineapple and onion; combine in a medium bowl with remaining 2 teaspoons lime juice, jalapeño, and 1/8 teaspoon salt. Sprinkle pork with 1/2 teaspoon salt and 1/4 teaspoon freshly ground black pepper. Heat grill pan over medium-high heat. Coat pan with cooking spray. Add pork; cook 4 minutes on each side or until done.
Seed the jalapeño if you prefer a milder salsa.