Line a rimmed baking sheet with aluminum foil or parchment paper and then spray it with nonstick cooking spray.
Cut the fish fillets into 6-ounce portions.
Sprinkle both sides of the fish pieces with salt and freshly ground black pepper.
In a wide bowl, combine the panko breadcrumbs and parsley.
Put the flour in another wide, shallow bowl.
In a third bowl, whisk the eggs or egg substitute with the Cajun seasoning and mayonnaise.
Dip the fish fillets in the plain flour, coating each piece thoroughly.
Dip the flour-coated fillets in the egg mixture and then coat them with the panko crumb mixture, pressing lightly to help the crumbs adhere to the fish. Repeat with the remaining fish.
Arrange the crumb-coated fish on the prepared baking sheet.
Bake for about 16 to 20 minutes, or until the fish flakes easily with a fork. The time in the oven depends on thickness, so adjust for very thin or very thick fish fillets. Serve the baked fish fillets with the lemon wedges and tartar sauce or rémoulade sauce.