Cook the elbow macaroni according to package instructions. Drain and let it cool.
In a large mixing bowl, whisk together mayonnaise, apple cider vinegar, and Dijon mustard until well combined.
Add the cooled macaroni to the bowl, tossing to coat it evenly with the dressing.
Gently fold in grated carrots, chopped onions, and celery.
Use salt and pepper to season the salad. Adjust the seasoning as needed.
Refrigerate the macaroni salad for at least an hour to let the flavors meld.
Before serving, give the salad a final toss and adjust the consistency with a little more mayonnaise or vinegar if desired.