Preheat the oven to 400°F (205°C). Pat the seabass fillets dry with paper towels and season both sides with 1 tsp kosher salt and 1 tsp freshly ground black pepper (divide evenly).

Make wine-butter sauce

In a medium skillet over medium heat, add 2 tablespoons olive oil. Add the minced garlic and cook 30–45 seconds until fragrant but not browned. Add 1 cup dry white wine and 2 tablespoons lemon juice. Bring to a gentle simmer and reduce by about one-third (3–5 minutes). Lower heat, whisk in 6 tablespoons unsalted butter a tablespoon at a time until the sauce is smooth and slightly thickened. Stir in chopped parsley and dill, taste and adjust seasoning.

Sear and bake

Heat a large oven-proof skillet (or transfer to a baking dish) over medium-high heat. Add a drizzle of olive oil. Sear seabass fillets skin-side down (if skin-on) for 2 minutes to get light color, then flip and sear 30–45 seconds. Pour the wine-butter sauce over and around the fillets, spooning some over the top. Transfer skillet to the preheated oven and bake until the fish is opaque and flakes easily, about 8–12 minutes depending on thickness (internal temp ~135–140°F/57–60°C). Remove from oven and let rest 2 minutes.

Sauteed Arugula & Caramelized Fennel

Caramelize fennel & onion

While oven preheats (or while fish bakes), heat a large sauté pan over medium heat. Add 2 tbsp olive oil and 1 tbsp unsalted butter. Add the thinly sliced fennel and sliced onion, season with 1 tsp kosher salt and 1/2 tsp black pepper. Cook, stirring occasionally, until softened and beginning to brown, 10–12 minutes. Sprinkle 1 tsp granulated sugar over the vegetables, stir to combine, then add 1 tsp white wine vinegar to deglaze and intensify flavor. Continue cooking another 2–3 minutes until caramelized but not burnt. Taste and adjust seasoning.

Wilt arugula

Push the caramelized fennel and onion to one side of the pan. Add the 6 cups arugula in batches, tossing with the fennel mixture and allowing it to wilt—about 1–2 minutes per batch. Season with a pinch more salt and pepper as needed. Remove from heat and keep warm.

Topping & Finish

Prepare orange and olives

Segment the navel orange over a small bowl to catch juices (use a sharp knife to cut away peel and pith, then slice between membranes to release segments). Reserve any juice. Pit and halve the Kalamata olives if not already done.

Assemble and finish

Place a mound of the warm sautéed arugula and caramelized fennel on each plate. Top with a baked seabass fillet. Spoon a few tablespoons of the white wine butter sauce from the pan over the fish. Scatter orange segments and halved Kalamata olives over the fish and greens. Drizzle 1–2 teaspoons of reserved orange juice into the remaining sauce pan, swirl to combine and spoon a little more over each portion if desired. Finish with chopped fennel fronds, 1/2 tsp finishing salt (divided), and a light grind of 1/4 tsp black pepper over all.

Serve

Serve immediately so the fish is warm and the arugula retains some bright peppery bite. Leftover sauce can be served on the side.