Sprinkle fillets with 1/4 teaspoon salt and 1/4 teaspoon black pepper.
Place on grill rack coated with cooking spray, and grill for 4 minutes on each side or until desired degree of doneness.
Place tomatoes, onion, and jalapeo on grill rack coated with cooking spray; grill tomatoes, cut side down, 6 minutes. Turn; grill for 1 minute. Grill onion and jalapeo for 6 minutes on each side or until lightly browned.
Remove from grill, and cool slightly. Coarsely chop tomatoes and onion; finely chop jalapeo.
Combine tomatoes, onion, jalapeo, 1/4 teaspoon salt, 1/4 teaspoon black pepper, and juice from 1/2 lime.