Preheat your oven to 400°F (204°C) and prepare your baking dish by greasing it with cooking spray or butter.

In a mixing bowl, whisk together melted butter, minced garlic, garlic powder, onion powder, lemon zest, lemon juice, and red pepper flakes.

Pat the cod fillets dry and toss them in the butter mixture until fully coated.

Transfer the coated fillets to the greased baking dish, pour any remaining sauce over them, and garnish with lemon slices.

Bake for 10-15 minutes until fish flakes easily, checking for an internal temperature of 145°F (63°C).

Remove from the oven, let rest for a couple of minutes, and sprinkle with chopped parsley before serving.