Grouper sandwich

Cook it at home: Blackened grouper sandwich with Key lime tartar

Blackening is a hot, fast sear in a dry cast-iron pan: the spice crust darkens while the fish stays moist inside. Grouper is firm and mild, so it holds together. Any thick, firm white fish works if you can't find it: mahi-mahi, snapper or cod. Open a window, it smokes.

Pans and tools

• Large cast-iron skillet
• Shallow dish
• Pastry brush
• Small bowl

You’ll need

• 4 grouper fillets, about 6 oz (170 g) each and 3/4 to 1 inch (2 to 2.5 cm) thick, skinless
• 2 tsp sweet paprika
• 1 tsp smoked paprika
• 1 tsp garlic powder
• 1 tsp onion powder
• 1 tsp dried thyme
• 1/2 tsp dried oregano
• 1/2 tsp cayenne pepper, or to taste
• 1 tsp kosher salt
• 1/2 tsp freshly ground black pepper
• 3 tbsp (45 g) unsalted butter, melted
• 1 tbsp neutral oil, such as canola
• 1/2 cup (115 g) mayonnaise
• 2 tbsp finely chopped dill pickle or relish
• 1 tbsp capers, chopped
• 1 tsp finely grated Key lime zest (or regular lime) and 1 tbsp juice
• 1 tsp Dijon mustard
• 4 soft brioche or Kaiser buns, split
• 4 leaves green-leaf lettuce
• 1 large ripe tomato, sliced
• Thin slices of red onion (optional)
• Lime wedges, to serve

Steps

1. Make the tartar: stir the mayonnaise, pickle, capers, lime zest and juice and mustard together. Chill while you cook.
2. Mix the paprikas, garlic powder, onion powder, thyme, oregano, cayenne, salt and black pepper in a shallow dish.
3. Pat the fillets very dry. Brush both sides with half the melted butter, then press them into the spice mix to coat all over.
4. Heat a large cast-iron skillet over high heat for 5 minutes, until very hot. Add the oil, swirl, then lay in the fillets, not touching.
5. Cook without moving for 3 to 4 minutes, until the underside is deep brown, almost black at the edges. Flip, drizzle the rest of the butter over the tops and cook 2 to 3 minutes more, until the fish flakes at the thickest part (145°F / 63°C).
6. While the fish rests 1 minute, toast the cut sides of the buns in a dry pan.
7. Spread tartar on both halves of each bun. Add lettuce, a fillet, tomato and onion. Serve with lime wedges and more tartar on the side.

Contains: ['fish', 'eggs', 'gluten', 'dairy', 'mustard'].

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