In a medium sized bowl, whisk together the mayonnaise (or yogurt), honey, lemon zest and juice, salt and pepper.
In a large bowl, combine apple, celery, grapes, and walnuts.
Pour dressing over salad and gently toss to combine.
Serve on a bed of fresh butter lettuce.
Notes
The best apples are crisp, sweet, juicy apples like a Fuji, Jonagold, or Honeycrisp. I prefer to leave the skin on for extra color and flavor. Plain greek yogurt can be used in place of the mayonnaise, however you may need to add more honey to compensate for the tartness.