01 -
Stir mayo, pickle relish, Dijon, garlic powder, lemon juice, plus a bit of salt and pepper in a little bowl. Drop it in the fridge while you keep going.
02 -
Toss together flour, cornstarch, garlic powder, onion powder, smoked paprika, cayenne (if you want it hot), salt, and pepper. Pour cold club soda as you stir, till it's about like pancake batter.
03 -
Pour veggie oil in a big skillet now and crank it to medium-high. You want it hot—around 350°F. No thermometer? Flick in batter. If it sizzles, you're set.
04 -
Dry the cod, dunk it in the batter, and gently lay it into the hot pan. Let each side fry for 3-4 minutes till it looks crispy and golden. Pull out once it's cooked through, about 145°F, and pop it on paper towels.
05 -
While your fish sizzles, throw your buns cut side down on a pan or in the toaster till they're lightly browned and warm.
06 -
On the bottom bun, smear some tartar. Pile on lettuce, one tomato slice, and your favorite extras. Add your crunchy cod, press the top bun on, and you're good to go.
07 -
Eat right away. Squeeze some lemon over the fish for an extra zing if you like.