Press the tofu: Drain the tofu and wrap it in a clean kitchen towel.
Place a heavy skillet or books on top and press for 20–30 minutes to remove excess moisture. This helps it crisp up.
Slice the tofu: Cut the pressed tofu into slabs about 1/2-inch thick. You want sturdy pieces that won’t fall apart while frying.
Mix a quick marinade: In a bowl, whisk 1/2 cup buttermilk (or plant milk + 1 teaspoon lemon juice), 1 tablespoon hot sauce, 1 teaspoon Cajun seasoning, and a pinch of salt.
Add the tofu and let it soak for 15 minutes.
Make the remoulade: Stir together 1/2 cup mayo, 1 teaspoon Dijon, 1 teaspoon prepared horseradish, 1 tablespoon lemon juice, 1 tablespoon chopped pickles or relish, 1 teaspoon capers (optional), a few dashes hot sauce, 1/2 teaspoon paprika, 1/4 teaspoon garlic powder, and a pinch of cayenne. Taste and adjust salt and lemon. Chill until serving.
Prep the bread and toppings: Split the baguette, leaving a hinge if you like.
Warm it in a low oven for a few minutes to crisp the crust. Slice tomatoes, shred lettuce, and set out pickles and onions.
Set up the dredge: In a shallow dish, combine 1/2 cup cornmeal, 1/2 cup all-purpose flour, 1–2 teaspoons Cajun seasoning, 1/2 teaspoon garlic powder, 1/2 teaspoon onion powder, 1/2 teaspoon smoked paprika, and a good pinch of salt and pepper.
Coat the tofu: Lift each tofu slab from the marinade, let excess drip, then dredge in the cornmeal-flour mixture. Press lightly so the coating adheres.
Place on a plate to rest 5 minutes.
Fry the tofu: Heat about 1/4 inch of oil in a skillet over medium to medium-high. When shimmering, add tofu in batches. Fry 2–3 minutes per side until golden and crisp.
Transfer to a wire rack or paper towel and sprinkle with a little salt.
Assemble the sandwich: Generously spread remoulade on both sides of the warm bread. Layer lettuce, tomatoes, pickles, and red onion. Add the crispy tofu and another spoon of remoulade if you like heat.
A squeeze of lemon and a dash of hot sauce take it over the top.
Serve right away: Po’ boys are best when the tofu is still hot and the bread is crisp outside, soft inside.