Preheat oven to 500°. Place bell pepper on an aluminum foil-lined baking sheet, and bake, turning 4 times, for 45 minutes or until bell pepper looks blistered. Place bell pepper in a zip-top plastic freezer bag; seal and let stand 10 minutes. Peel, remove and discard seeds, and coarsely chop.
Reduce oven temperature to 450°. Arrange tomato and onion in a jelly-roll pan. Add garlic and olive oil, and toss to coat. Sprinkle with 1⁄2 tsp. each salt and black pepper. Bake at 450° for 45 minutes. Cool 15 minutes.
Transfer roasted bell pepper and tomato and onion mixture to a food processor bowl. Process 2 minutes or until smooth. Transfer to a Dutch oven, and add chicken broth. Bring to a boil over medium heat; reduce heat, and simmer 30 minutes or until thickened.
Toss bread pieces in melted butter. Sprinkle with cheese and remaining 1⁄4 tsp. each salt and black pepper. Arrange in a jelly-roll pan. Bake at 450° for 5 minutes or until crisp.