Preheat the oven to 375 degrees F (190 degrees C).
Combine pistachios, panko bread crumbs, Parmesan cheese, and butter in a small bowl; stir with a fork until evenly combined.
Lightly season salmon fillets with salt and pepper on both sides.
Heat olive oil in a large oven-safe skillet over medium heat. Sear salmon fillets, flesh-side down, for 2 to 3 minutes. Turn heat off and flip salmon pieces over so skin side is down. Brush tops of salmon evenly with Dijon mustard. Top with pistachio mixture, pressing mixture down onto salmon.
Bake in the preheated oven until salmon flakes easily with a fork, 10 to 12 minutes. Serve with lemon wedges.