When done, pat them dry. You want your fillets to be roughly the same thickness, as this ensures that they all cook at the same rate in the oven. Get out a baking dish and line it with parchment paper so the cod do not stick to the bottom while cooking. Mix 1-2 teaspoons of salt and pepper in a small bowl and apply this to both sides of the fish, sprinkling it on top. There is no "right" amount to use, but when in doubt go light -- you can always add more before serving. Place the fillets in the baking dish when you are done. If you have coarse or kosher salt, use this instead of table salt. The larger grains of salt will not dissolve as quickly, leading to a more even flavor in the fish. In a small bowl, stir together 1 tablespoon of butter and lemon juice and a dash of onion or garlic powder  This is a good time to add any additional seasonings you enjoy. Try out a teaspoon of chili powder, paprika, and/or cayenne for a hotter fish, or oregano, rosemary, thyme, and/or basil for an Italian herb mixture. While you can substitute some olive oil for butter, the fat in butter is essential for keeping the fish moist and flaky. Place small dollops of the mixture over the fish and use a rubber spatula to evenly coat the tops of the fish. As the fish cooks the butter will melt into the flakes of the fish, coating the inside for a moist, silky, and flaky texture at the end. When the fish is done the white flesh will easily flake off when pulled with a fork. There should be big full flakes when the fish is cut, not a thin crumb-like texture.. You can quickly adapt this recipe to get surprising new flavors with your main dish:  Cook the cod with chopped vegetables, such as  1 large tomato, 1 green bell pepper, 1 yellow squash or zucchini, 1/2 cup pitted Kalamata olives, halved, and cloves garlic, all finely chopped, for a full one-pan meal. Toss the veggies with 1 tablespoon olive oil and place them around the fish, letting them cook simultaneously.  Chop up 1/2 cup of fresh parsley and add it to your butter mixture...

TL;DR in Vietnamese:
Rửa và rã đông cá tuyết phi lê. Làm nóng lò ở 180ºC và chuẩn bị khay nướng. Rắc muối và tiêu lên hai mặt của miếng cá. Trộn bơ hoặc bơ thực vật mềm với nước cốt chanh. Phết hỗn hợp bơ/bơ thực vật lên miếng cá phi lê. Nướng cá khoảng 15-20 phút. Biến tấu món cá tuyết nướng.