In a large bowl, combine the mayonnaise, honey, Dijon mustard, apple cider vinegar, garlic powder, salt, and black pepper. Whisk until smooth and well blended.
Add the cooked chicken to the bowl and stir until the chicken is evenly coated with the honey mustard dressing.
In a separate large serving bowl, place the mixed salad greens, cherry tomatoes, cucumber, and red onion.
Top the salad with the honey mustard chicken mixture. If desired, sprinkle with chopped walnuts or pecans for added crunch.
Toss gently to combine just before serving, ensuring the dressing is evenly distributed.