Place a dry, large cast iron or heavy nonstick frying pan over medium-high heat. Add the corn and cook, stirring often, until the corn begins to brown, 4 to 5 minutes. Remove from the heat and set aside.
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, 1/2 teaspoon of the salt, 1/4 teaspoon of the black pepper and the cilantro. Pulse to blend. Set the vinaigrette aside.
Prepare a hot fire in a charcoal grill or preheat a gas grill or broiler (grill). Away from the heat source, lightly coat the grill rack or broiler pan with cooking spray. Position the cooking rack 4 to 6 inches from the heat source.
In a small bowl, mix together the cumin, oregano, red pepper flakes and the remaining 1/2 teaspoon salt and 1/4 teaspoon black pepper. Rub on both sides of the steak. Place the steak on the grill rack or broiler pan and grill or broil, turning once, until browned, 4 to 5 minutes on each side. Cut into the center to check for doneness (medium doneness is 160 F if using a meat thermometer). Let stand for 5 minutes. Cut across the grain into thin slices. Cut the slices into pieces 2 inches long.
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.
To serve, divide the salad among individual plates. Top each serving with slices of grilled steak.