Whisk eggs, flour, garlic powder, salt, and pepper in one bowl. Place panko in another.
Pat fillets dry, season, dip in egg-flour mix, then coat with panko.
Add 6 mm oil to a skillet and heat over medium until shimmering.
Fry fillets 2–3 minutes per side until golden and crispy. Drain on paper towels and sprinkle with salt.
On a toasted bun, layer cheese, hot fish, tartar sauce, and top bun.
Enjoy immediately with fries, slaw, or chips.