Place the pieces in a shallow dish. Combine lemon juice, minced garlic, 1 tsp kosher salt, 1 tsp freshly ground black pepper and 1 tbs olive oil. Pour over the fish and let marinate for 10–15 minutes in the refrigerator while you prepare breading and sauce.

Tartar-style sauce

In a small bowl, stir together 1/2 cup mayonnaise, 2 tsp dill pickle relish, 1 tsp chopped capers, 1/2 tsp lemon zest, 1/4 tsp hot sauce (if using), 1/4 tsp salt and 1/4 tsp black pepper. Taste and adjust seasoning. Refrigerate until ready to assemble.

Breading and cooking (pan-fry)

Set up a dredging station: in one shallow bowl combine 1 cup all-purpose flour, 1 tsp salt, 1 tsp black pepper and 1/2 tsp paprika. In a second bowl whisk 2 eggs with 1/2 cup buttermilk. In a third bowl combine 1 cup fine cornmeal.

Remove fish from the marinade and let excess liquid drip off. Dredge each piece first in flour (shake off excess), then dip in the egg-buttermilk, then press into cornmeal to coat completely. Shake off loose crumbs.

Heat a large skillet over medium-high heat and add about 1/4–1/2 cup vegetable oil to reach a thin layer (enough to shallow-fry). When oil is shimmering (around 350°F / 175°C), add the fillets without crowding the pan. Cook 3–4 minutes per side until golden brown and the interior reaches 145°F (opaque and flakes easily). Transfer to a wire rack set over a baking sheet and keep warm in a 200°F oven if needed.

Toasting buns & assembly

Split the 4 sandwich rolls or brioche buns and spread softened butter on cut sides. Toast in a skillet or under a broiler until golden, about 1–2 minutes per side.

Spread 1–2 tablespoons of the tartar-style sauce on the bottom half of each bun. Place a lettuce leaf on top of the sauce, then a piece of cooked grouper, a slice of tomato, and pickles if using. Spoon a little more sauce on the top bun and close the sandwich.

Serve immediately with lemon wedges on the side and optional fries or chips.