Clean the lettuce, wash and spin dry. Roast the walnuts in a pan and set aside. If necessary, wash the apple, rub dry and quarter. Remove the core and cut into fine slices.
Dressing:
Mix buttermilk, vinegar and oil vigorously and season with salt and pepper.
Finishing:
Finally mix the salad, walnuts, apple slices and cranberries with the dressing.