Preheat the oven to 400 degrees F. Grease a rimmed baking sheet with cooking spray. Place the grated Parmesan on a dinner plate and add the garlic powder and paprika.
Wash the lemon and pat it dry. Cut it in half and make zest from one of the halves by using a zester or grater to shave off the yellow part of the skin, adding it to the cheese mixture.
Rinse the parsley and pat it dry. Cut it with scissors or chop it before adding it to the cheese mixture. Toss the cheese mixture with a fork to blend it.
Rinse the fish in cold water and rub your thumbs along the surface to see if there are any bones to remove. Pat the fish dry with paper towels.
Melt the butter in a small pan on the stove or microwave it in a bowl. Set up an assembly line from left to right with the fish, the butter, the cheese mixture, and the sheet pan.
Use a fork to dip each piece of fish in the butter on both sides, then in the cheese mixture, coating both sides and patting the topping onto the cod with the fork. Place the coated fish onto the sheet pan, top with any excess melted butter and bake for 15 minutes. The cod is done when it can be easily flaked with a fork.
Squeeze lemon juice over the fish and serve with bread for dipping in the garlic butter (you can place the pan on the table for informal dinners) or spoon the butter over rice, mashed potatoes or polenta. Store leftover cod in the refrigerator for up to three days.
* I use salted butter and find this dish is salty enough with the Parmesan. If you're using unsalted butter, you'll need to add salt.