1/2 cup mayonnaise
1/4 cup dijon mustard
1/4 cup brown sugar
4 tablespoons cider vinegar
2 tablespoons buttermilk
1 teaspoon celery seeds
1/2 teaspoon black pepper
2 bags Rainbow slaw mix
1/2 medium sweet onion thinly sliced
1 cup blue cheese crumbled
Combine all ingredients in a arge bowl. Stir well to coat. Refrigerate until chilled. Serve cold.