Begin by bringing a large pot of generously salted water to a boil. Add elbow macaroni and cook according to package instructions until al dente, typically around 8-10 minutes. Once cooked, drain in a colander and rinse under cold water.

In a medium mixing bowl, whisk together mayonnaise, Dijon mustard, apple cider vinegar, sugar, salt, and black pepper until smooth and well combined. Set aside while you chop the vegetables.

Finely dice the celery, green bell pepper, and red onion into uniform pieces, ensuring they are small enough to mix seamlessly into the salad.

In a large mixing bowl, gently fold the cooled macaroni into the diced vegetables. Pour the creamy dressing over and gently toss to combine.

Cover the bowl tightly and refrigerate for at least 2 hours before serving. Stir gently before serving to redistribute the dressing.