Preheat oven to 425°.
Remove stem end from tomatoes; place in colander and rinse under cold running water. Drain well.
Place tomatoes in a bowl; drizzle with oil, and sprinkle with salt and cumin. Toss gently. Place tomato mixture on a large jelly roll pan coated with cooking spray. Bake at 425° for 14 minutes or until tomatoes begin to shrivel and juices evaporate. Transfer tomatoes to a small bowl. Add onion, cilantro, lime juice, and garlic. Toss gently. Cool to room temperature; cover and chill until ready to serve.