Wash all produce thoroughly. Core and julienne the apples (leave the skin on for extra color and nutrition), then immediately toss them with 1 tablespoon of lemon juice to prevent browning.
Shred the cabbage finely using a sharp knife or food processor. Use the large holes on a box grater for the carrots if you don't have pre-shredded ones.
In a large bowl, whisk together the mayonnaise, apple cider vinegar, honey, Dijon mustard, celery seeds, salt, pepper, and garlic powder until completely smooth.
Add the shredded cabbage, julienned apples, carrots, red onion, and parsley to the bowl with the dressing.
Using tongs or two large spoons, gently toss until all ingredients are evenly coated. Be careful not to crush or break the delicate vegetables.
Cover the bowl and refrigerate for at least 30 minutes before serving to allow the flavors to meld.
Just before serving, give the coleslaw another gentle toss. If using any of the optional add-ins like dried cranberries or toasted nuts, fold them in now.
Taste and adjust seasonings if needed before serving.