01 - Preheat oven to 400°F and lightly grease a baking dish large enough to hold fillets in a single layer.
02 - Pat haddock fillets dry with paper towels and place them in the prepared baking dish.
03 - Combine olive oil, lemon juice, lemon zest, minced garlic, sea salt, and black pepper in a small bowl; whisk until blended.
04 - Drizzle the olive oil mixture evenly over the haddock fillets.
05 - Sprinkle drained capers and chopped parsley over the fillets.
06 - Bake for 16 to 18 minutes, or until the fish flakes easily with a fork and is opaque throughout.
07 - Serve immediately, garnished with additional parsley and lemon slices, if desired.