How to Make It
Heat a large skillet over medium-high. Coat pan with cooking spray. Sprinkle steak with 1/4 teaspoon salt and 1/4 teaspoon pepper. Add steak to pan; cook 5 minutes on each side or until desired degree of doneness. Place steak on a cutting board; let stand 5 minutes. Cut across the grain into slices; cut slices into 3/4-inch pieces.
Add oil to pan; swirl. Add onion; sauté 2 minutes. Add 1/4 teaspoon salt, stock, and beans to pan; bring to a boil. Cook 4 minutes, scraping pan to loosen browned bits.
Divide lettuce among 4 shallow bowls. Top evenly with bean mixture, steak, tomato, tortilla chips, and avocado. Sprinkle with remaining 1/4 teaspoon salt, remaining 1/4 teaspoon pepper, and queso fresco. Serve with lime wedges.