01 -
In a large mixing bowl, combine the shredded cabbages, carrots, and red onion.
02 -
In a separate small bowl, whisk together mayonnaise, apple cider vinegar, mustard, sugar, celery seed (if using), salt, and pepper until smooth.
03 -
Pour the dressing over the vegetables and toss well until fully coated.
04 -
Taste and adjust seasoning if needed.
05 -
For best flavor, cover and refrigerate for at least 1 hour before serving.