Blackened Swordfish Sandwich Recipe

Prepare fish

Pat the swordfish steaks dry with paper towels. If using a whole pound, cut into 4 sandwich-sized pieces (about 4 oz each). Let sit at room temperature for 10 minutes.

Make blackening spice

In a small bowl combine paprika, smoked paprika, garlic powder, onion powder, oregano, thyme, cayenne, kosher salt, and black pepper. Mix thoroughly.

Season fish

Brush both sides of each swordfish steak lightly with olive oil, then press the blackening spice onto both sides so a thin, even coating adheres.

Heat a heavy cast-iron skillet or nonstick pan over medium-high heat until very hot (about 3–5 minutes). Add a thin film of oil if the pan is not well seasoned. When shimmering, add the swordfish steaks (do not overcrowd — cook in batches if necessary).

Cook the steaks 3–4 minutes per side for 1-inch thick pieces, without moving them, until a dark crust forms (blackened) and the internal temperature reaches 130–135°F (54–57°C) for medium. Thicker steaks may need an extra minute per side. Avoid overcooking — swordfish should be opaque and just firm.

Transfer cooked steaks to a plate, tent loosely with foil and rest 3–4 minutes.

In a small bowl, combine mayonnaise, dill pickle relish, lemon juice, chopped capers (if using), chopped parsley, Dijon mustard, salt, and black pepper. Stir until smooth and taste; adjust lemon, salt or relish to preference. Refrigerate until ready to use.

Toast buns: Split buns and spread butter on cut sides. Place in a hot skillet or on a griddle, buttered side down, and toast until golden (about 1–2 minutes).

Arrange: Spread 1 to 2 tablespoons of tartar sauce on the bottom half of each bun. Place a lettuce leaf on the sauce, then set a rested blackened swordfish steak on top. Add 2–3 tomato slices and a few rings of red onion. Add additional tartar on the top bun if desired.

Serve immediately with your choice of side (fries, salad, or chips). Each sandwich serves one; this recipe makes about 4 sandwiches.