For a flavorful dinner, grilled salmon is rubbed with a mixture of toasted black mustard seeds and ground coriander and cumin. Tamarind-Date Chutney is the perfect complement to the fish.
Place the mustard seeds in a small, dry heavy skillet. Place skillet over medium heat, moving skillet to keep seeds from burning, until seeds are toasted, about 5 minutes. Transfer mustard seeds to a small bowl. Place coriander and cumin seeds in the skillet. Toast over medium heat, shaking skillet to move the seeds, until they are aromatic, 3 minutes. Transfer these seeds to a spice grinder, and grind until fine. Transfer mixture to the bowl with the mustard seeds; stir in the salt, turmeric, and peppercorns.
Place the salmon on a clean work surface. Rub skin side with 1 tablespoon oil, and turn salmon over. Use your fingers to spread the spice rub all over the flesh side of the salmon. (If the salmon is chilled, let sit 10 to 15 minutes at room temperature for even cooking.) Rub grill very well with the oil; heat until very hot. Grill the salmon, flesh-side down, until flesh turns opaque about halfway up the fish, 5 to 10 minutes. Use two large spatulas to turn over the fish. Cook just until fish is opaque throughout and still very moist, 5 to 15 minutes more. Transfer to a platter; garnish with fresh chiles (if using) and lime wedges. Serve with Tamarind-Date Chutney.