1. Heat large cast iron or heavy nonstick frying pan over medium-high heat. Add the corn and toast, stirring often, until the corn begins to brown (4-5 minutes). Remove from the heat and set aside.
2. In a food processor, combine the stock, lime juice, bell pepper, and 1 cup of the roasted corn. Pulse to puree. Add the olive oil, half of the salt and pepper, and the cilantro. Pulse to blend. Set the vinaigrette aside.
3. Preheat a grill to high and oil the rack.
4. Mix together the cumin, oregano, red pepper flakes, and the remaining salt and pepper. Rub on both sides of the steak.
5. Grill the steak, turning once, until browned (4-5 minutes per side). Test temperature for preferred doneness.
6. Let steak rest for 5 minutes then slice into strips.
7. In a large bowl, combine the lettuce, tomatoes, onion, black beans, and remaining roasted corn. Add the vinaigrette and toss gently to mix well and coat evenly. Top salad with sliced steak to serve.