For the slaw: Combine the cabbage, carrots and red onions in a large bowl and toss gently.
For the dressing: Whisk together the mayonnaise, buttermilk, dry rub, vinegar, sugar and salt to taste (about 1/2 teaspoon) in a bowl until smooth.
Add the dressing to the slaw and toss gently until completely coated. Cover and refrigerate for 2 to 3 hours before serving.
Combine the brown sugar and cornstarch in a bowl and mix by hand until the lumps are gone. (This is a great trick for preventing clumps in brown sugar.)
Combine the paprika, garlic salt, seasoned salt, 1 cup of the brown sugar mixture, the granulated sugar, chili powder, black and white peppers, allspice, cayenne, cumin and mustard powder in a large bowl. Mix until well blended. Apply the rub liberally to meats with a shaker prior to smoking, for a true Kansas City BBQ taste.
Dry rubs vary in saltiness. Be careful not to oversalt the dressing if you are using a different dry rub.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Momma's Mustard, Pickles and BBQ, Louisville, KY