Pat the swordfish steaks dry with paper towels. In a shallow dish, combine 2 tbs olive oil, 1 tbs fresh lemon juice, 1 tsp minced garlic, 1 tsp smoked paprika, 3 tsp coarse salt and 1 tsp black pepper. Rub the marinade over both sides of the swordfish. Cover and refrigerate for 20–30 minutes (no longer than 1 hour) to allow flavor to penetrate.

Pastrami Spice Coating

Make the pastrami-style rub

While the fish marinates, mix 2 tbs coarsely ground black pepper, 1 tbs crushed coriander seeds, 1 tsp smoked paprika, 1 tsp brown sugar, 1 tsp mustard powder, 1 tsp garlic powder and 1 tsp kosher salt in a small bowl. Use the back of a spoon to press and roughly combine the spices so the mix is slightly coarse and holds together.

Coat the swordfish

Remove the swordfish from the marinade and let excess drip off. Press the pastrami spice mixture onto both sides of each steak, creating an even, coarse crust. Allow the coated steaks to sit at room temperature for 5–10 minutes while you heat the pan.

Cooking the Swordfish

Preheat and sear

Heat a large heavy skillet or cast-iron pan over medium-high heat until hot. Add 1 tbs neutral oil and 1 tbs butter (optional) and swirl to coat. Place the coated swordfish steaks in the pan, pressing briefly so the crust makes contact. Sear without moving for 2–3 minutes until a dark crust forms.

Finish cooking

Flip the steaks and reduce heat to medium. Cook another 2–4 minutes, depending on thickness, until the fish registers 130–135°F (54–57°C) for medium and is opaque but still moist. Remove to a plate and tent with foil for 3 minutes to rest. If you prefer cheese melted on top, place Swiss slices on the steaks in the last minute of cooking and cover briefly to melt.

Bread & Assembly Prep

Toast and butter bread

While the fish rests, spread softened butter evenly on the cut sides of the ciabatta rolls. Toast the rolls, buttered side down, in a clean skillet over medium heat until golden and crisp, about 1–2 minutes. Alternatively, toast in a 400°F (200°C) oven for 4–6 minutes.

Make sauce

In a small bowl, stir together 2 tbs mayonnaise, 2 tbs prepared mustard and 1 tsp chopped fresh dill (if using). Adjust salt and pepper to taste.

Final Assembly & Serve

Spread a thin layer of the mustard-mayo sauce on both cut sides of each toasted roll. Place the pastrami-coated swordfish steak on the bottom half of each roll. Top with an additional slice of Swiss cheese if you didn’t melt it on the fish, then pile on 1/4 cup thinly sliced dill pickles or 1/4 cup drained sauerkraut per sandwich. Add the top roll, press gently and slice in half if desired.

Serve immediately with lemon wedges on the side. Squeeze a little lemon over the fish just before eating for brightness. Pass extra mustard or pickles on the side.