The sea dog (a fried fish sandwich) is not really a thing but should definitely be a thing because it’s that good. (If you’ve been to the Red Rooster on route 22 in Brewster, NY, you already know this is true.) The batter alone should become your go-to whenever you fry fish.
- 1 pound skinless, boneless cod fillet, cut crosswise into 8 strips
- Kosher salt, freshly ground black pepper
- 1 tablespoon Old Bay seasoning
- 2 teaspoons baking powder
- ¼ teaspoon cayenne pepper
- 3 tablespoons malt or cider vinegar
- Vegetable oil (for frying; about 3 quarts)
- 8 New England–style split-top hot dog buns
- 4 tablespoons unsalted butter, room temperature
- Tartar Sauce, shredded lettuce, and lemon wedges (for serving)
Lightly season cod with salt and black pepper. Transfer to a wire rack set inside a rimmed baking sheet. Chill, uncovered, at least 1 hour or up to overnight (this air-dries the surface so the batter will adhere better to the fish).
Whisk flour, cornstarch, Old Bay, baking powder, paprika, garlic powder, onion powder, baking soda, cayenne, 2½ tsp. salt, and ½ tsp. black pepper in a medium bowl. Add beer and vinegar and whisk just until combined and no lumps remain.
Fit a large heavy pot with thermometer; pour in oil to a depth of 3". Heat over medium-high until thermometer registers 375°. Working in batches, dip fish into batter, allowing excess batter to drip back into bowl. Lower carefully into oil and fry until light golden brown and just cooked through, 3–4 minutes. Transfer to paper towels to drain.
Heat a large skillet over medium. Spread bottom and sides of each bun with butter. Toast buns, pressing down lightly, until golden, about 2 minutes per side.
Generously spread some tartar sauce in each bun; top with lettuce and a fried fish fillet. Serve with lemon wedges and additional tartar sauce alongside.