Prep the tofu. Pat the tofu dry with paper towels or a clean, lint-free kitchen towel — the drier the surface, the better the crust. Choose your shape: cut into 1/2" steaks, tear into bite-sized pieces, or cube.
Coat with soy sauce. If using steaks, brush each one on both sides with soy sauce. If using smaller pieces, add them to a bowl and toss with 1 tablespoon soy sauce. This will help the seasoning adhere.
Make the spice blend. Mix all the spices and nutritional yeast together in a wide, shallow dish. Press or dip each piece into the seasoning until well coated on all sides. Set aside on the dish or a plate while you heat the pan.
Heat the pan. Add 1-2 tablespoons of neutral oil to your cast iron over medium heat. Let it heat until the oil shimmers and a piece of tofu sizzles immediately when it touches the pan — you want hot enough to sear, but not so hot that it smokes.
Sear. Add the tofu in a single layer, working in batches if needed — don't crowd the pan. For steaks, sear undisturbed for 3-4 minutes per side until deeply charred and crusty, flipping once. For smaller pieces, toss occasionally until all sides are well seared.
Rest and serve. Let the tofu rest for a minute or two before serving over rice or grains. A squeeze of fresh lime and some sliced green onion make a great finishing touch.