Combine mayo, dill relish, lemon juice, parsley, sugar, mustard, dill, onion powder, red pepper flakes, and black pepper in a bowl. Mix until smooth and thick.

In one bowl, mix all-purpose flour, salt, black pepper, and chili powder.

In another bowl, whisk together eggs, salt, chili powder, and black pepper.

Blend panko breadcrumbs, salt, chili powder, and black pepper until sandy. Transfer to a bowl.

Dip each fish fillet in flour, then egg, and finally coat with panko mix, using separate hands for dry and wet.

Heat vegetable oil to 325°F.

Carefully fry fillets for 8 to 9 minutes until golden and cooked through.

Drain excess oil on a wire rack, then top each fillet with American cheese.

On toasted buns, assemble fish, cheese, tartar sauce, and lettuce if desired.

Close sandwiches and savor every bite!