Slice the kanpachi fillets into strips about 1-inch by 2-inches. Season lightly with kosher salt and set aside while you make your batter.
Add one cup of flour to a medium mixing bowl and the remaining half cup of flour to a plate.
To make the batter, slowly pour in the beer to the bowl with the flour, about ½ cup at a time, and whisk to combine. Continue adding beer until the batter is mostly smooth with a few small lumps. Set aside the batter while you finish prepping, or store in the fridge tightly covered overnight.
Add the zest to the plate with the flour. Sprinkle the garlic powder and salt over as well, then stir to thoroughly combine with a fork.
Add the oil to a deep-sided pan or pot, and heat over medium-high until shimmering. Test if the oil is ready by adding a pinch of flour: if it sizzles, the oil is ready! Set up a station for the fish to drain on once it’s done cooking by placing a rack over a sheet pan.
Dredge the fish strips in the dry flour mixture on the plate, tapping off any excess flour before dipping into the batter. Make sure the fish strips are completely coated in batter, then allow any excess to drip off before carefully dropping into the hot oil.
Fry fish in batches, a few strips at a time, being careful not to overcrowd the pan. Use tongs to turn fish strips as they turn golden, then remove to the rack to drain once they’re cooked on all sides. Season with a pinch of salt once they’re on the rack. Let the fish cool slightly before plating up your tacos!
