Is there a better “newish” hand-held food than fish tacos? Battered or baked, spicy or not… someone was using their brain when they decided tacos deserved a pairing with those aquatic craniate animals. This version goes back to the origins: Fish tacos were born in the Baja area. The first fish tacos were like these: a delicate fish lightly battered and fried, served in a tortilla with a mayo slaw. Are we reinventing perfection here? No, we are sharing it with you.
Halve and peel onion. Slice halves into thin strips. Halve limes and juice three halves. Halve remaining lime piece. Mince cilantro (no need to stem). Pat tilapia fillets dry and, on a separate cutting board, cut into 2" pieces. Season pieces with ¼ tsp. salt and ¼ tsp. pepper.
Quick Pickle Onion and Make Slaw
Combine onion, 2 Tbsp. lime juice, and a pinch of salt in a small mixing bowl. Combine slaw mix and mayonnaise in another small mixing bowl and add Sriracha (to taste). Refrigerate both.
Make the Batter
Combine tempura mix and ⅓ cup very cold water in a medium mixing bowl. Stir until batter is extremely thin, almost the consistency of water. If needed, add water 1 Tbsp. at a time until desired consistency is reached.
Warm the Tortillas
Place a large non-stick pan over medium heat. Place tortillas in hot, dry pan and cook until warmed, 30 seconds per side. Alternatively, wrap tortillas in a paper towel and microwave, 30-60 seconds. Wrap tortillas in foil to keep warm. Reserve pan; no need to wipe clean. Line a plate with a paper towel.
Cook the Fish
Return pan used to warm tortillas to medium-high heat and add canola oil. Add tilapia pieces to batter and cover pieces evenly. Test oil temperature by adding a drop of batter to it. It should sizzle gently. If it browns immediately, turn heat down and let oil cool. Carefully, working in batches, add tilapia pieces to hot oil and cook until golden brown and pieces reach a minimum internal temperature of 145 degrees, 2-3 minutes per side. Transfer to towel-lined plate, and season with a pinch of salt.
Plate the Dish
Place warm tortilla on a clean surface. Add tilapia, slaw, pickled onion (to taste), and top with cilantro. Repeat with remaining tortillas. Place three tacos on a plate and serve with lime wedge on the side.