A simple yogurt sauce pairs nicely with broiled salmon; this elegant main dish comes together easily in about 15 minutes.
Make sauce: Stir together yogurt, chopped tarragon, and lemon zest and juice; season with salt and pepper.
Heat broiler, with rack set 4 inches from heat. Line a rimmed baking sheet with aluminum foil. Place salmon on sheet, and season with salt and pepper. Broil until opaque throughout, 8 to 10 minutes. (Keep at room temperature up to 1 hour.) Serve salmon, garnished with tarragon leaves, with sauce alongside.
Sauce can be refrigerated up to 1 day.