Preheat your grill or stovetop 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 all over the flank steak.

Grill the steak for about 5-7 minutes on each side for medium-rare, or until your desired doneness. Remove from the grill and let it rest for 5 minutes before slicing it thinly against the grain.

While the steak is resting, add the sliced bell peppers and onion to the grill. Cook for about 5-7 minutes until they are tender and slightly charred.

In a separate bowl, whisk together the sour cream, mayonnaise, cilantro, lime juice, garlic powder, salt, and pepper to make the dressing.

In a large bowl, combine the mixed greens, grilled vegetables, avocado, and cherry tomatoes. Toss gently to combine.

Top the salad with the sliced steak and drizzle with the creamy cilantro lime dressing before serving.