01 - Preheat the oven to 400°F. Lightly grease a baking dish large enough to hold the fillets in a single layer.
02 - Pat haddock fillets dry with paper towels. Arrange fillets in the prepared baking dish. Drizzle olive oil over the fish and season both sides with salt and black pepper.
03 - In a small bowl, combine melted butter, lemon juice, lemon zest, capers, parsley, and minced garlic. Stir until thoroughly mixed.
04 - Spoon the lemon-caper mixture evenly over the haddock fillets, ensuring full coverage.
05 - Bake in the preheated oven for 15 to 18 minutes, or until the fish becomes opaque and flakes easily with a fork.
06 - Garnish with fresh lemon slices and additional parsley if desired. Serve immediately.