Season the chicken with 1/2 teaspoon salt, chili powder, paprika, and cayenne.
Heat a large skillet over medium heat and add the oil. When shimmering, add the chicken to the pan and cook until it lifts easily with a spatula. Flip, and continue cooking until a thermometer inserted in the center reaches 165 degrees F. Remove from pan and set aside while you make the salad.
Salad
In a large bowl, toss together the lettuce, corn, tomatoes, onions, salsa, and cheese. Divide salad between 6 plates. Slice the chicken and add it to the salad.
Mash the avocado with the lime juice and remaining salt, and add to the salads with the sour cream.