Score both sides of steak in a diamond pattern by making shallow diagonal cuts at 1-inch intervals. Place beef on a tray or in a dish. Sprinkle Baja Rub evenly over both sides of steak; rub in with your fingers. Let stand for 10 minutes.
Meanwhile, for dressing, in a medium saucepan heat oil over medium-high heat. Add garlic; cook for 30 seconds. Add broth, lime juice, chile pepper, smoked paprika, salt, and black pepper. Bring to boiling; reduce heat. Boil gently, uncovered, for 5 to 7 minutes or until mixture is reduced to 1/2 cup, stirring occasionally.
For a charcoal grill, grill steak on the rack of an uncovered grill directly over medium coals for 17 to 21 minutes or until steak reaches medium doneness (160 degrees F). Remove steak from grill. Cover and set aside. Place romaine wedges on grill rack over coals. Grill about 3 minutes or until lettuce is wilted and browned, turning once. Transfer to a serving platter or plates. (For a gas grill, preheat grill. Reduce heat to medium. Add beef, and then romaine, to grill rack. Cover and grill as above.)
Thinly slice flank steak across the grain. Serve with romaine wedges. Top salads with avocados, tomatoes, cilantro, cheese, and green onions. Pass dressing.
In a small bowl combine kosher salt, garlic powder, smoked paprika, ground black pepper, ground cumin, and cayenne pepper. Mix well.