Pat the cod fillets completely dry with paper towels. Moisture on the surface of the fish will prevent the breadcrumb crust from sticking and can make it fall off during cooking. Season both sides lightly with a pinch of salt and pepper.

In a small bowl, combine the panko breadcrumbs, olive oil, lemon zest, dried parsley, garlic powder, salt, pepper, and paprika. Stir until the olive oil is evenly distributed and the breadcrumbs look lightly coated. The mixture should hold together loosely when pressed.

Brush a thin layer of Dijon mustard over the top of each cod fillet. This acts as the glue that holds the breadcrumb mixture in place. You do not need much, just a thin even coat over the top surface.

Press the breadcrumb mixture firmly onto the mustard-coated top of each fillet using your fingers or the back of a spoon. Press it down so it adheres, not just sits on top. A firmly pressed coating stays on during cooking, a loosely placed one ends up on the basket floor.

Preheat your air fryer to 400 degrees F for 3 minutes. Lightly spray the basket with cooking spray to prevent sticking. Place the fillets in the basket crust side UP in a single layer, not touching each other.

Air fry at 400 degrees F for 10 to 12 minutes without flipping. You want to leave the crust undisturbed so it forms a solid golden layer. The fish is done when the breadcrumbs are deep golden brown and the cod flakes easily when you press the thickest part gently with a fork.

Use a thin spatula to carefully lift each fillet out of the basket. Serve immediately with roasted green beans, a simple tomato salad, or lemon wedges for squeezing over the top. The crust will stay crispy for about 10 minutes after cooking.