Begin by bringing a large pot of salted water to a rolling boil over high heat. Once boiling, add the ditalini pasta and cook for about 7–9 minutes, or until al dente. Drain the pasta in a colander, then rinse it thoroughly under cold water.

In a spacious mixing bowl, combine the mayonnaise, Dijon mustard, cider vinegar, sugar, salt, and grated onion. Whisk together until smooth and creamy, then add celery seeds and black pepper, mixing well.

Once the ditalini pasta has cooled, transfer it into the bowl with the coleslaw dressing. Toss gently until evenly coated.

Carefully add the coleslaw mix to the pasta salad, folding gently to maintain crispness of the vegetables.

Taste and adjust seasoning as necessary, adding extra salt or sugar for balance.

Cover and chill the pasta salad in the refrigerator for at least 30 minutes before serving.