1. Preheat grill to medium-high heat.
2. Brush cut sides of tomatoes and onion slices with 1 tablespoon oil. Lightly coat bread with cooking spray. Place bread on grill rack, and grill 1 1/2 minutes on each side or until toasted. Remove from grill. Place peppers on grill rack coated with cooking spray. Grill 8 minutes or until blistered, turning peppers after 4 minutes. Remove peppers from grill. Place peppers in a small paper bag; fold tightly to seal. Let stand for 20 minutes. Arrange onion on grill rack; grill for 10 minutes. Turn onion over. Arrange tomatoes, cut sides down, on grill rack; grill onion and tomatoes 10 minutes. Peel and seed peppers.
3. Combine 2 tablespoons oil, bread, grilled vegetables, 1/2 cup water, 2 tablespoons juice, 1/2 teaspoon salt, black pepper, and garlic in a blender; process until smooth. Combine the remaining 1 tablespoon olive oil, remaining 1 1/2 teaspoons lemon juice, remaining 1/4 teaspoon salt, cucumber, and remaining ingredients; toss. Ladle about 2/3 cup soup in each of 6 bowls, and top each serving with about 1/3 cup cucumber mixture.