Using the shredding disc attachment (also called the grating dish), shred 6-cups of green or purple cabbage. Shred carrot next. Once done, transfer to a large bowl and toss cabbage and carrot together.
In a small bowl, whisk together mayonnaise, sour cream, cider vinegar, sweetener, celery seed, mustard powder and salt.
Pour dressing over cabbage. Mix until thoroughly combined.
Refrigerate at least 30 minutes, up to 12 hours before serving for flavors to blend. The longer this chills, the better the texture and flavor.