Preheat the grill or a grill pan over medium-high heat. In a small bowl, mix the olive oil, chili powder, cumin, garlic powder, salt, and pepper. Brush the mixture over both sides of the salmon fillets.
Place the salmon on the grill and cook for about 4-5 minutes per side, or until the salmon is cooked through and flakes easily with a fork. Remove from heat 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 over the salad and toss gently to combine. If desired, add ranch dressing for extra creaminess.
Serve immediately, or chill in the refrigerator for 15-30 minutes for a refreshing cold salad.