Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper for easier cleanup.
In a mixing bowl, combine grated Parmesan cheese, breadcrumbs, fresh parsley, lemon zest, minced garlic, red pepper flakes, salt, and pepper. Mix until well incorporated to create the crust mixture.
Pat the cod fillets dry with paper towels and season each side lightly with salt and pepper.
Spread a thin layer of Dijon mustard over the top of each cod fillet; this will help the crust adhere and enhance the flavor.
Press the Parmesan breadcrumb mixture onto the mustard-coated side of the cod fillets to create a thick crust. Be generous!
Drizzle a bit of olive oil over the crusted cod for added richness and to help achieve a golden color.
Place the cod fillets on the prepared baking sheet and bake in the preheated oven for 12-15 minutes, or until the fish is cooked through (internal temperature of 145°F) and the crust is golden brown.
Once done, let the cod rest for a couple of minutes before serving to retain its juices.
Notes
Serve on a bed of lemon-herb quinoa and garnish with lemon wedges and parsley.