Grilled Haddock Sandwich Recipe

Prepare the fish

Pat the haddock fillets dry with paper towels. If the fillets are thick, cut them into sandwich-sized portions (about 4 equal pieces total).

Marinate

In a shallow bowl, whisk together 2 tablespoons olive oil, 1 tablespoon lemon juice, 1 teaspoon minced garlic, 1 teaspoon smoked paprika, 1 teaspoon kosher salt, and 1 teaspoon black pepper. Place the haddock pieces in the bowl and turn to coat. Let sit at room temperature for 10 minutes (or refrigerate for up to 30 minutes).

Preheat grill or pan

Preheat a grill or grill pan over medium-high heat (about 400°F / 200°C) and oil the grates or pan lightly to prevent sticking.

Grill the haddock

Brush off excess marinade and place the haddock on the hot grill or pan. Cook 3–4 minutes per side, depending on thickness, until the fish flakes easily with a fork and reaches an opaque center (internal temperature about 145°F / 63°C). Remove from heat and let rest 2 minutes.

Flake for sandwich

If you prefer a flaky sandwich filling instead of whole fillets, break the cooked haddock into large flakes with a spatula while warm.

In a small bowl, combine 1/2 cup mayonnaise, 2 tablespoons finely chopped dill pickle, 1 tablespoon chopped capers, 1 teaspoon lemon zest, 1 teaspoon fresh lemon juice, 1 teaspoon chopped fresh dill or parsley, 1/2 teaspoon Dijon mustard, 1/4 teaspoon salt, and 1/4 teaspoon black pepper. Stir until smooth and taste; adjust salt, lemon, or dill to preference. Chill in the refrigerator while finishing the fish if time allows.

Prepare vegetables and rolls

Slice the tomato into 4 even slices; thinly slice the red onion into rings. Split the 4 rolls and spread a thin layer of softened butter on the cut sides.

Toast the rolls (optional): Place buttered cut sides down on the grill or a skillet over medium heat and toast until golden, about 1–2 minutes.

Assemble the sandwiches: Spread about 1 to 1 1/2 tablespoons of the tartar-style sauce on the bottom half of each roll. Place a lettuce leaf on top of the sauce, then a portion of grilled haddock (whole fillet or flaked, about 4 oz cooked haddock per sandwich). Add a tomato slice, a few red onion rings, and two pickle slices. Spoon a little extra sauce on the top half of the roll if desired, then close the sandwich.

Serve immediately: Serve warm with lemon wedges on the side for squeezing, and additional pickles or chips as a side.