Press extra firm tofu thoroughly — wrap in clean kitchen towel or several layers of paper towels place on a plate with a heavy skillet or cutting board on top and press for minimum 15–20 minutes to remove as much moisture as possible.
While tofu presses make quick pickles first — place thinly sliced purple cabbage and red onion in a heatproof bowl with whole coriander seeds, star anise, and black peppercorns.
In a small saucepan combine apple cider vinegar, water, salt, and sugar and bring to a boil over medium heat stirring until salt and sugar are completely dissolved.
Pour hot pickling liquid directly over vegetables and spices and allow to cool completely to room temperature — vegetables will turn vivid pink-purple as they cool — rest minimum 30 minutes before using.
Preheat oven to 350°F (180°C).
After pressing cut tofu into large thick steak-like slabs or chunks.
Sprinkle cornstarch evenly over tofu pieces and press gently to ensure complete even coating on all surfaces with no bare spots.
Place coated tofu in a single layer on a baking tray with space between each piece — do not crowd.
Drizzle with 1 tablespoon vegetable oil and bake for 20–30 minutes until lightly golden and exterior has a slightly firm crispy quality — flip once halfway through for even browning.
While tofu bakes whisk together light soy sauce, mirin, maple syrup, tomato paste, smoked paprika, cornstarch, and water in a small bowl until completely smooth — set sauce aside.
Heat a skillet or wok over medium-high heat and add a small splash of oil if needed.
Add thinly sliced green onion and ginger and sauté for 1–2 minutes until fragrant and lightly softened.
Add baked tofu pieces to the pan and pour BBQ glaze sauce over tofu.
Let sauce come to a simmer and reduce for 2–3 minutes tossing tofu gently to coat every piece in the glossy sticky glaze — watch carefully as cornstarch thickens sauce quickly.
Remove from heat when sauce has reduced to a thick glossy coating on all tofu pieces.
Steam bao buns according to package directions — typically 8–10 minutes in a steamer basket until soft pillowy and fully heated through — steam frozen bao directly from frozen with no thawing needed.
Split each steamed bao bun open gently.
Place one or two pieces of BBQ glazed tofu steak inside each bun.
Add a generous tangle of quick-pickled purple cabbage and red onion.
Layer in a few thin slices of fresh cucumber.
Garnish with thinly sliced green onion, fresh chili rings, and a scatter of sesame seeds.
Serve immediately while bao is warm and tofu is still glazed and glossy.