For marinade, in a small bowl stir together tomato sauce, tomato paste, the water, mustard, Worcestershire sauce, honey, and chipotle peppers. Set aside. Trim fat from steak. Score both sides of steak in a diamond pattern by making shallow diagonal cuts at 1-inch intervals. Place steak in a large resealable plastic bag set in a shallow dish. Pour marinade over steak in bag. Seal bag; turn to coat steak. Marinate steak in the refrigerator for 4 to 6 hours, turning bag occasionally.
Drain steak, reserving marinade. Lightly coat sweet pepper quarters and onion slices with nonstick cooking spray.
For a charcoal grill, grill steak, sweet pepper quarters, and onion slices on the rack of an uncovered grill directly over medium coals until steak is medium doneness (160 degrees F) and vegetables are tender, turning once halfway through grilling. Allow 17 to 21 minutes for the steak and 8 to 12 minutes for the vegetables. (For a gas grill, preheat grill. Reduce heat to medium. Place steak, sweet pepper quarters, and onion slices on grill rack over heat. Cover and grill as directed.)
Meanwhile, for sauce, pour reserved marinade into a small saucepan. Bring to boiling; reduce heat. Simmer, uncovered, about 5 minutes or until desired consistency.
Let steak stand for 5 minutes. Thinly slice steak across the grain. Thinly slice sweet pepper quarters lengthwise. Place steak slices and sweet pepper strips on the bottom halves of the ciabatta rolls. Top with onion slices. Spoon sauce over onions. Add ciabatta roll tops.