Heat a cast iron skillet on medium heat. Add butter to skillet and heat until just before burning.
Season the chicken breasts and place in hot butter. Cook for about 3 minutes. Turn over and cook the other side for about 3 minutes. Turn every 3 minutes after, cooking until the internal temperature of chicken is 165 degrees Fahrenheit in the thickest part.
Set the chicken aside and allow to rest for 10 minutes.
While the chicken is resting, prepare the salad. Cut the lettuce into 1/2" strips, tearing it apart and placing in a large bowl. Add the Parmesan cheese, salad dressing, and lemon juice. Toss them to coat evenly. Salt and pepper to taste.
Slice rested chicken breasts into 1/4" strips. Add croutons and chicken immediately before serving.