Preheat your Oven to 400°F. Lightly grease a Baking Dish with a little 3 tbsp extra-virgin olive oil. Pat the 1 ½ lb cod fillets about 4 fillets, patted dry completely dry with Paper Towel — this helps them bake rather than steam.

In a small Mixing Bowl, whisk together the 3 tbsp extra-virgin olive oil, 3 cloves garlic minced minced, 1 whole lemon zested and sliced into rounds zest, 1 tsp smoked paprika, ½ tsp dried oregano, ½ tsp fine sea salt, ¼ tsp freshly ground black pepper, and ¼ tsp red pepper flakes (if using). Spoon and spread this mixture evenly over the top of each 1 ½ lb cod fillets about 4 fillets, patted dry.

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, 1 whole lemon zested and sliced into rounds 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.