Cook the elbow macaroni according to package instructions until al dente. Drain and rinse under cold water to cool.
In a large mixing bowl, combine the mayonnaise, Dijon mustard, apple cider vinegar, garlic powder, onion powder, salt, and black pepper. Mix until smooth.
Add the cooled macaroni to the bowl with the dressing and stir to coat evenly.
Fold in the diced celery, bell pepper, red onion, sweet pickle relish, and parsley. Mix until all ingredients are well combined.
If using, sprinkle the grated Parmesan cheese over the top and gently mix it in.
Cover the bowl with plastic wrap and refrigerate for at least 1 hour to allow the flavors to meld. Serve chilled.