1. Heat a grill pan over medium-high heat. Combine 1 teaspoon oil, 1/2 teaspoon salt, cumin, chile powder, and pepper; rub evenly over steak. Add steak to pan; cook 6 minutes on each side or until desired degree of doneness. Remove steak from pan; let stand 5 minutes. Cut steak diagonally across grain into thin slices.
2. While steak rests, brush remaining 1 tablespoon oil over both sides of polenta slices; sprinkle evenly with remaining 1/4 teaspoon salt. Add polenta to pan; cook 3 minutes on each side or until browned. Arrange 2 polenta slices on each of 4 plates; divide avocado evenly among servings. Top each serving with about 3 ounces steak, 2 tablespoons cilantro leaves, 2 tablespoons queso fresco, and 2 tablespoons salsa. Serve with lime wedges, if desired.