Poached Salmon with Watercress and Peaches

Poach salmon: In a large straight-sided skillet, combine 6 cups water, lemon slices, peppercorns, and 1 1/2 teaspoons salt; bring to a simmer over medium-high, then reduce heat to a low simmer. Add salmon (water should just cover fish), cover, and cook until opaque throughout, 5 to 8 minutes. With a wide, slotted spatula, transfer salmon to a plate.

To serve: Whisk together lemon zest and juice, oil, and mustard; season with salt and pepper. Divide watercress, peaches, and basil among 4 plates, top with salmon, and drizzle with dressing. Season with salt and pepper.