Combine 1/4 cup basil, lemon rind, lemon juice, and 2 minced garlic cloves in a shallow dish. Add fish, and turn to coat. Cover and chill 30 minutes.
Combine tomato, olives, capers, remaining 1 minced garlic clove, remaining 1/4 cup basil, and 1/8 teaspoon pepper in a medium bowl.
Place fish on grill rack coated with cooking spray. Grill 3 to 4 minutes on each side or until desired degree of doneness. Sprinkle fish with salt and remaining 1/8 teaspoon pepper. Serve with salsa.