In a food processor combine cilantro, Greek yogurt, garlic, lime juice, and salt.
With the motor running add the olive oil and vinegar in a slow stream until emulsified. Set aside.
In a small bowl combine chili powder, ground cumin, coriander, brown sugar, cayenne pepper, and 1 tablespoon of olive oil. Mix well. Rub the spice mixture onto both sides of the chicken breasts.
Lightly grease the grates of an outdoor grill. Heat the grill to medium-high heat. Add the chicken breasts to the grill and cook, turning at least once until the chicken is fully cooked (the internal temperature has reached 165 Degrees F.).
Remove the chicken from the grill and allow it to cool for 10 minutes. After the chicken has cooled slice it into thin strips.
Place romaine lettuce into a large bowl. Top with tomatoes, corn, black beans, cheese, and grilled chicken. Pour the dressing over the top of the salad and gently toss to combine.