Drain canned tuna thoroughly — press firmly in a Colander or squeeze in a paper towel to remove as much liquid as possible. Excess moisture prevents browning. Mix drained tuna with mayo, lemon juice, salt, pepper, and any mix-ins like celery, pickles, or red onion. If making a sandwich melt, butter one side of each bread slice and set aside. Slice your cheese and have everything ready before the Skillet heats up — cook time moves fast.

Preheat a Skillet over medium heat for about 1 minute. Medium heat is key — too high burns the bread before the cheese melts, too low gives soggy results. For a tuna melt sandwich: Assemble with tuna on the unbuttered side of the bread, add tomato slices if using, then layer on two slices of cheese. Top with the second slice buttered side up. Place in the skillet cheese side down. Cook undisturbed 3 to 4 minutes until deep golden brown on the bottom. Flip and cook another 3 to 4 minutes until the second side is golden and cheese is fully melted. Total cook time is 4 to 8 minutes depending on pan, heat, and bread thickness. For loose tuna without bread: Add tuna mixture directly to the preheated skillet over medium heat. Stir and cook about 5 minutes until heated through and moisture has cooked off, stirring occasionally to prevent sticking.

Pat the 4 cod fillets about 6 oz each, patted dry completely dry with paper towels — this is key for a good texture and helps the 3 tbsp unsalted butter melted sauce cling to the fish. Season both sides lightly with ¾ tsp kosher salt and ½ tsp black pepper freshly ground, then arrange them in the prepared Baking Dish.

In a small Mixing Bowl, whisk together the melted 3 tbsp unsalted butter melted, 2 tbsp olive oil, minced 3 cloves garlic minced, 1 lemon zested and juiced (about 3 tbsp juice), 1 lemon zested and juiced (about 3 tbsp juice), 2 tbsp fresh parsley finely chopped, 1 tbsp fresh dill finely chopped (if using), dried 1 tsp dried oregano, ¼ tsp paprika sweet or smoked, ¾ tsp kosher salt, and ½ tsp black pepper freshly ground until combined.

Bake uncovered for 12–15 minutes, depending on the thickness of your fillets. The fish is done when it flakes easily with a fork and is opaque all the way through. A 1-inch thick fillet takes about 15 minutes. Do not overbake — cod turns dry and rubbery quickly.

Remove from the Oven and let rest for 2 minutes. Spoon the pan juices over the fillets, scatter with fresh Parsley, and serve immediately with your choice of sides.