Core tomatoes, and cut each in half crosswise; push seeds out of middle section with thumbs. Set tomatoes aside. Peel onion, leaving root intact; cut into 6 wedges. Place the tomato halves and onion wedges on a broiler pan coated with cooking spray; broil 5 minutes. Turn vegetables over; broil 5 minutes or until tomatoes are tender and onion is slightly blackened. Trim root from the onion wedges. Place the tomatoes and onion wedges in a food processor; pulse 3 times or until chopped. Set aside.
Heat oil in a large nonstick skillet over medium heat. Add jalapeño and garlic; sauté 30 seconds. Add tomato mixture, cilantro, lime juice, salt, and pepper; cook over medium-low heat 3 minutes or until thoroughly heated.