Heat grill. In small bowl, combine chili powder, cumin, 1 teaspoon brown sugar and ground red pepper; mix well. Place halibut on large plate. Brush both sides of fish with lime juice; sprinkle both sides with chili powder mixture. Let stand at room temperature for 10 minutes to marinate.
Meanwhile, in medium bowl, combine all salsa ingredients; mix well.
When ready to grill, carefully oil grill rack. Place fish on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Cook 10 to 14 minutes or until fish flakes easily with fork, turning once. Serve salsa with fish. If desired, garnish with chopped fresh cilantro.