Place the baking rack on the top shelf. Preheat the oven to 425°F (220°C).
Pat dry cod fillets with paper towels, season with salt and pepper on both sides. Place on a baking sheet lined with parchment paper.
In a small bowl, stir together grated parmesan, breadcrumbs, lemon zest, pressed garlic cloves, chopped parsley, and olive oil. Season with salt and pepper.
Divide the parmesan mixture on top of each fillet, press the mixture so it stays on the fish.
Bake for 9-10 minutes or until almost done, the fish is not translucent but white and flakes easily.
The baking time may vary depending on the thickness of fish fillets. The best way to check if your fish is done is to check its temperature with a thermometer. I like to use a grill thermometer, I'm inserting the probe into the thickest part of the thinnest fillet. A thin wire goes through the oven door to the thermometer that stays on the outside. This type of thermometer measures the temperature inside of the fish for the whole cooking process. I'm taking the fish out when the temperature reaches 131°F (55°C) and it finishes cooking while resting (it really goes quickly for fish). The fish is safe to eat when the temperature in its thickest part reaches 145°F (63°C) although I usually eat it at 140°F (60°C). If your fish fillets vary in thickness, take out thinner fillets when they're done and continue cooking thicker fillets. It's really important to not overcook the fish - it will be rubbery and tough.
Enjoy!