In a medium bowl, combine mayonnaise, apple cider vinegar, Dijon mustard, sugar, sea salt, and black pepper. Whisk until smooth and creamy.

Shred green cabbage and red cabbage, julienne or shred carrots, and thinly slice red onion. Place all in a large mixing bowl.

Pour dressing over the vegetables and toss gently until evenly coated.

Cover with plastic wrap and refrigerate for at least 1 hour before serving.