Cut tofu cake horizontally into 3/4 inch thick rectangles (about the size of your buns).
Cover the bottom of a small pan with half of barbecue sauce. One by one, rub both sides of each tofu rectangle with chile powder; place in a single layer on sauce. Top with remaining sauce. Let stand for 30 minutes.
Meanwhile, make slaw: Mix all ingredients (except for cabbage/slaw) together in a small bowl. Let sit for 5 minutes. Mix sauce into cabbage and chill until ready to use.
Preheat broiler with rack 6 inches from heat. Line a baking sheet with aluminum foil; place a baking rack on top. Spray rack with cooking spray. Take tofu slabs out of the barbecue sauce and place on rack with space between pieces. Reserve leftover barbecue sauce. Broil until top of tofu is browned and bubbly, about 5 minutes. Turn tofu over. Broil until browned and bubbly, about 5 more minutes.
Toast the buns, place tofu, more sauce (if desired), pickles and a scoop of slaw on top of each sandwich.