Preheat your oven to 425°F and let it come to full temperature while you prep the fish.
Line a large rimmed baking sheet with foil or parchment paper, then spray generously with cooking spray. This prevents sticking and makes cleanup easier.
Cut the fish into 6-ounce portions — about 4-5 inches long and evenly sized so they cook at the same rate.
Season both sides of each fillet with salt and pepper, pressing gently so the seasoning adheres to the surface.
Mix the panko and chopped parsley in a wide, shallow bowl. The parsley adds color and fresh flavor to the crust.
Place the flour in a separate shallow bowl for the first coating station.
In a third bowl, whisk together the eggs, Cajun seasoning, and mayonnaise until smooth. The mayo helps the coating stick and adds richness.
Dredge each piece of fish in flour, shaking off any excess. The flour creates a base layer that helps the egg mixture cling.
Dip the floured fish into the egg mixture, letting excess drip off, then press into the panko mixture on both sides. Really press to make sure the coating adheres well.
Place the breaded fillets on your prepared baking sheet with space between each piece for even browning.
Bake for 16-20 minutes until the coating is golden brown and the fish flakes easily when tested with a fork at the thickest part.
⏱ 20 min
While the fish bakes, cut the lemon into 4 wedges for serving.
Serve immediately with lemon wedges for squeezing and tartar sauce on the side if desired.