How to Make It
Microwave the kombu in 10-second bursts at medium power for 30 seconds; be careful not to let it scorch. Let cool completely until crisp. Break the kombu into pieces and grind to a powder in a spice grinder. In a small bowl, combine the softened butter with the kombu powder.
Preheat the oven to 375°. Heat a large skillet. Rub the iceberg wedges lightly with oil and season with salt and pepper. Add them to the skillet and cook over moderately high heat, turning once, until lightly charred, about 2 minutes. Transfer to a platter, cover loosely with foil and keep warm.
In the same skillet, melt 2 tablespoons of the kombu butter. Add the asparagus and cook over moderately high heat, turning occasionally, until tender and browned in spots, about 4 minutes. Add the vinegar and toss; keep warm.
In an ovenproof nonstick or cast-iron skillet, heat the 2 tablespoons of oil until shimmering. Season the fish fillets with salt and pepper and add them to the skillet, skin side down. Set another skillet on top of the fish and cook over moderately high heat for 1 minute to flatten and sear the skin. Remove the top skillet and cook the fish until browned on the bottom, about 2 minutes longer. Transfer the skillet to the oven and roast the fish until cooked through, about 5 minutes.
Return the skillet to moderate heat and add 3 tablespoons of the kombu butter. Spoon the melted butter all over the fish. Arrange the fish, lettuce and asparagus on plates. Spoon the remaining 3 tablespoons of kombu butter on top. Garnish with nori and sprinkle with sea salt. Serve at once, with lemon wedges.
Kombu is available at Japanese markets, health-food stores and some supermarkets as well as online at edenfoods.com.