Butterfly chicken breast and dust with salt and pepper.
Bake in oven at 350° F until cooked completely (30-45 mins.)
Let chicken cool then dice chicken into mout sized pieces.
Add onions, celery, and mayo (consistency should be moist not soupy)
Set aside in refrigerator for flavors to develope.
Serve in tomato cups, bed of lettuce, or on your favorite bread/crossiant.