Steamed Salmon with Watercress and Lemon Butter

In a large pot, bring about 1 inch of water to a boil. Put the fish in a large steamer basket, skin-side down; sprinkle with 1/4 teaspoon of the salt and 1/4 teaspoon pepper. Pile the watercress on top. Sprinkle with another 1/4 teaspoon salt.

Put the steamer basket with the fish over the boiling water and cover. Reduce the heat to moderately high and cook until the watercress is wilted and the salmon is just barely done (the fish should still be translucent in the center), about 5 minutes for a 1-inch-thick fillet.

Meanwhile, in a small stainless-steel saucepan, melt the butter. Add the lemon juice, the remaining 1/4 teaspoon salt, and a pinch of pepper. Serve the salmon and watercress topped with the lemon butter.