Shred the green and red cabbage. I find the best way to do this is to use a mandolin slicer on a fine setting. (Use the safety guard to protect your fingers!) You can also do it carefully with a large chef’s knife. Then shred the carrots using a box grater.
Set out a large mixing bowl. Add both kinds of shredded cabbage and the carrots. Toss well.
In a separate bowl or measuring pitcher, combine the mayonnaise, lemon juice, rice vinegar, sugar, salt, black pepper, celery seeds, and onion powder. Mix until smooth.
Pour the dressing over the coleslaw mix. Toss well to fully coat. Then cover and refrigerate for at least 30 minutes.
