Unsalted butter, for baking dish
1/2 cup pitted and sliced Kalamata olives
2 teaspoons drained capers, rinsed and coarsely chopped
2 anchovy fillets, rinsed, drained, and coarsely chopped
1 garlic clove, minced
1 teaspoon fresh lemon juice, plus several thinly sliced lemon rounds, halved if large
3 tablespoons extra-virgin olive oil
1 tablespoon chopped fresh oregano, plus small leaves for garnish
4 fish fillets
Preheat oven to 200o C. Butter a baking dish; set aside.
Stir together olives, capers, anchovies, garlic, lemon juice, oil, and oregano in a small bowl; set aside.
Season fish with salt and pepper; place in baking dish. Scatter olive mixture evenly over fish. Top with lemon slices.
Cover dish with foil. Bake until fish is firm, flaky, and cooked through, 15 to 17 minutes. Let rest 5 minutes before serving. Serve drizzled with juices from dish. Garnish with oregano leaves.