Preheat the oven to 180°C (350°F). Line a baking sheet with parchment paper or lightly grease it.
In a food processor, add 100 grams of shelled pistachios and pulse until coarsely ground. Transfer the ground pistachios to a shallow dish.
In a small bowl, mix 2 tablespoons of Dijon mustard, 1 tablespoon of honey, 1 teaspoon of grated lemon zest, and 1 tablespoon of lemon juice. Stir well to combine.
Take 4 salmon fillets (about 150 grams each) and pat them dry with a paper towel. Season both sides of the fillets with salt and pepper to taste.
Spread the mustard mixture evenly over the top of each salmon fillet.
Press the mustard-coated side of each fillet into the ground pistachios, ensuring an even coating.
Place the pistachio-crusted salmon fillets on the prepared baking sheet, crust-side up.
Bake in the preheated oven for 12-15 minutes, or until the salmon flakes easily with a fork and the pistachio crust is golden brown.