Pat the thawed fish dry and check for pin bones. Keep it refrigerated while preparing the sauce. Slice the onion, mince the garlic and chop the tomatoes.

Warm the olive oil in a 12-inch deep skillet over medium heat. Add the onion and cook for 5–6 minutes until softened without dark browning. Stir in the garlic for 30 seconds.

Add the tomatoes, olives, capers, oregano, bay leaf, salt, pepper and optional jalapeño. Simmer uncovered for 12–15 minutes, stirring occasionally, until the tomatoes soften into a chunky sauce. Add a tablespoon or two of water only if the pan becomes dry.

Nestle the fillets into the sauce and spoon some sauce over them. Cover, reduce the heat to medium-low, and cook gently for about 8–12 minutes, depending on thickness. Avoid stirring or repeatedly flipping the fish.

Check the thickest part of each fillet with a thermometer; it should reach 145°F (63°C). Remove finished pieces rather than overcooking them while thicker ones finish. Discard the bay leaf and serve the fish and sauce with optional lime wedges.

Refrigerate leftovers in a shallow covered container within 2 hours, or 1 hour above 90°F (32°C). Store at 40°F (4°C) or colder for 3–4 days. Reheat to 165°F (74°C), adding a little water if the sauce has thickened.