Pat salmon fillets dry with paper towels. Season both sides with kosher salt (about 1/4 tsp per side) and freshly ground black pepper. Let rest at room temperature for 10 minutes while you prepare the spinach.

Sear

Heat 2 tablespoons olive oil in a large nonstick or stainless steel skillet over medium-high heat until shimmering. Add the salmon fillets skin-side down and press gently with a spatula for 15 seconds to ensure even contact. Cook skin-side down for 4–5 minutes without moving, until the skin is crisp and the fish is cooked about two-thirds of the way up the sides.

Finish

Flip the fillets gently, add 1 tablespoon butter to the pan and spoon the melted butter over the tops while cooking for 1–2 minutes more, cooking to medium (internal temperature 125–130°F / 51–54°C) or longer if you prefer. Remove salmon to a warm plate, tent loosely with foil and squeeze half a lemon over the fillets.

Spinach & Sauce

Sauté aromatics

In a separate large skillet, heat 1 tablespoon extra virgin olive oil over medium heat. Add the finely chopped shallot and cook, stirring, for 1–2 minutes until softened. Add the minced garlic and cook for 30–45 seconds until fragrant but not browned.

Wilt spinach

Add the baby spinach in batches, letting each addition wilt slightly before adding more. Use tongs to turn and collapse the leaves. Total cooking time for the spinach will be about 3–4 minutes.

Make creamy sauce

Lower heat to medium-low. Stir in 1 tablespoon heavy cream and 2 tablespoons grated Parmesan. Cook for 30–60 seconds to warm the cream and melt the cheese. Season with 1 teaspoon salt, 1/2 teaspoon freshly ground black pepper and a pinch (1/8 tsp) of freshly grated nutmeg if using. Taste and adjust seasoning. If the mixture seems dry, add 1–2 tablespoons warm water or more cream to loosen.

Combine and keep warm

If desired, add a small knob of butter (about 1/2 tablespoon) and stir until glossy. Keep the spinach over very low heat until the salmon is ready to serve.

Plating & Finish

Divide the creamy spinach among 4 plates. Place a salmon fillet on top of each bed of spinach, skin-side up for presentation. Squeeze a lemon wedge over each portion, sprinkle with chopped fresh parsley, and serve immediately.