1. Make the tartar sauce.
Mix mayonnaise, pickles, dill, capers, and green onions in a bowl. Season with salt and pepper. Chill until ready to serve.
2. Make the Nashville butter.
In a small bowl, whisk together melted butter, cayenne, brown sugar, smoked paprika, chili powder, garlic powder, black pepper, and salt until smooth.
If it looks too thick or clumpy, whisk in a little more melted butter until it loosens up. Keep warm — you’ll brush it on the fish right after frying.
3. Prepare the batter.
Whisk together rice flour, all-purpose flour, baking powder, and a pinch of salt. Gradually whisk in beer until smooth and light — thick enough to coat evenly, but not heavy.
4. Toast the buns.
Butter the brioche buns and toast them in a hot pan until golden brown. Keep warm and ready for assembly.
5. Batter and bread the fish.
Pat cod fillets dry; season with salt and pepper. Dredge in rice flour, dip into beer batter, let excess drip off, then coat evenly in panko breadcrumbs.
6. Fry the fish.
Heat peanut oil to 350°F. Fry 3–4 minutes per side, until golden and crisp. Transfer to a wire rack to drain.
Brush generously with the warm Nashville butter while the fish is still hot.
7. Build the sandwich.
Follow this order for the perfect bite every time:
Bottom bun → tartar sauce → lettuce → fish → slice of cheddar (we melt ours with a kitchen torch) → more tartar sauce → top bun.
Serve immediately while everything’s hot and crisp.