In a small bowl; combine turnip, carrot, vinegar, cilantro, mayonnaise, and maple syrup. Stir to combine; season with salt and pepper, and refrigerate until needed.
Preheat oven to 450°.
In a small bowl; combine mustard, water, tamari, cumin, and liquid smoke. Whisk to combine; set aside.
Cut bottom stem and leaves from cauliflower. Stand cauliflower on it’s base; vertically, cut into four equal sections. Season one side of each slice with salt and pepper.
In a large pan, heat oil over medium temperature. Place cauliflower slices, seasoned side down, in pan and cook for 2-3 minutes, or until golden. While cooking on seasoned side, brush other side with bbq sauce.
Flip slices to sauced side down, and cook for 2 minutes.
Flip slices bbq side up, and place in preheated oven. Roast for 8-10 minutes, or until tender.
Top cauliflower with slaw. If desired, add additional bbq sauce and chives.