Preheat the grill or a grill pan over medium-high heat.
In a small bowl, mix together the olive oil, chili powder, cumin, garlic powder, salt, and pepper. Rub this mixture over the salmon fillets.
Grill the salmon for about 4-5 minutes per side, or until it flakes easily with a fork. Remove from the grill and let it rest for a few minutes.
In a large bowl, combine the mixed salad greens, cherry tomatoes, corn, avocado, black beans, red onion, and cilantro.
Flake the grilled salmon into bite-sized pieces and add it to the salad.
Drizzle the lime juice and ranch dressing over the salad and toss gently to combine.
Serve immediately, or chill in the refrigerator for 15-20 minutes for a refreshing cold salad.