Make dressing. In a small bowl make the dressing by combining the mayonnaise, buttermilk, sugar, lemon juice, onion powder, white vinegar, salt, and pepper. Stir until well combined.

Toss and chill. Pour the dressing over the cabbage and carrot mix and toss together. Cover bowl with plastic wrap and place in the refrigerator to chill for 1 hour. After coleslaw is chilled stir well and serve with a slotted spoon to strain out any excess liquid.