Mahi Mahi Sandwich Recipe

Prepare fish

Pat the mahi mahi fillets dry with paper towels and cut into 4 equal portions (about 4–5 oz each).

Season & dredge

In a small bowl mix kosher salt, black pepper, garlic powder, and smoked paprika. Lightly season both sides of each fish portion. Spread the all-purpose flour on a plate and dredge each fillet, shaking off excess.

Cook fish

Heat 1 tablespoon olive oil and 1 tablespoon butter in a large skillet over medium-high heat until shimmering. Add the fillets (do not overcrowd) and cook 3–4 minutes per side until golden and just cooked through (internal temperature ~145°F / 63°C). If fillets are thick, reduce heat to medium and cover for 1–2 minutes to finish. Transfer cooked fish to a plate and squeeze 1 tablespoon lemon juice over them.

Toast buns

Lower heat to medium. Add remaining 1 tablespoon butter and 1 tablespoon olive oil to the same skillet. Split buns and toast cut sides down 1–2 minutes until golden and slightly crisp.

Prepare vegetables

While fish cooks, slice tomato into 1/4-inch rounds and thinly slice the red onion. Tear/prepare lettuce leaves and season tomato lightly with a pinch of salt.

Assemble sandwiches

Spread about 2 tablespoons of tartar-style sauce onto the bottom half of each toasted bun. Place a lettuce leaf on each, followed by a cooked mahi mahi portion, a tomato slice, and a few slices of red onion. Add a drizzle of hot sauce if using. Cap with the top bun and serve immediately with lemon wedges.

Combine mayonnaise, dill pickle relish, chopped capers, fresh lemon juice, Dijon mustard, chopped dill (or parsley), black pepper, and salt in a small bowl. Whisk until smooth and taste; adjust salt, lemon, or relish to preference. Chill at least 10 minutes to let flavors meld (can be made up to 1 day ahead).

Serve sandwiches with lemon wedges for extra brightness and hot sauce on the side for guests who want heat.