Place first 3 ingredients on grill rack over medium-high heat (400°), cut sides up. Grill 4 minutes; remove jalapeño, and turn tomato and onion. Grill 4 more minutes.
Remove stem from tomato. Combine all ingredients except cilantro in container of a food processor; pulse until mixture is finely chopped. Pour mixture into a bowl; stir in cilantro.
Whisknladle, La Jolla, California