Preheat the grill to medium-high heat.
In a medium bowl, combine the chopped pistachios, brown sugar, lemon juice, dill (if using), and black pepper until evenly mixed.
Spoon the pistachio mixture evenly over the top of each salmon fillet and press gently so it adheres.
If using, line a grilling basket with foil and spray lightly with cooking spray to prevent sticking; otherwise place fillets directly on the grill grates.
Place the salmon on the hot grill, cover, and cook for 5 to 10 minutes, or until the salmon flakes easily with a fork and is cooked through.