Preheat your oven's broiler. Sprinkle salt and pepper over both sides of the chicken (if the chicken breast is too thick, then cut it in half horizontally). Place the chicken on a broiler pan coated with cooking spray; broil 5 minutes on each side or until the chicken is done. Cut the chicken into ¼-inch-thick slices.
Combine the chicken, spinach, apple, bell pepper, celery and onion in a large bowl. Drizzle the dressing over the salad, and toss well. Sprinkle with cheese and almonds.