Cook the elbow macaroni for 12-14 minutes. You want it to be quite soft. Drain and rinse in warm water, then sprinkle with 1 tbsp apple cider vinegar and stir. Let stand to drip.

While the mac is going, grate the onion and carrot on the large side of a box grater. Finely chop the celery. Stir together the mayonnaise, veg, salt, and pepper well, then fold in the macaroni.

Refrigerate for at least 1 hour to allow the flavors to develop. Serve slightly chilled by removing from the refrigerator 10 minutes before serving.