Preheat the oven to 375℉ and set the rack to the middle position. Lightly spray an oven-safe frying pan or other baking pan.
Rinse the salmon fillets and pat them dry with a paper towel. Sprinkle half of the salt and pepper over the top and place them inside the frying pan. Set the salmon aside.
Chop the pistachios finely.
In a small bowl, combine the mustard, lemon juice, olive oil, and honey. Whisk well to combine. Add any remaining salt and pepper, the lemon zest, minced garlic, and oregano. Mix well to combine all of the ingredients.
Add the chopped nuts to the bowl and stir well with a spatula or spoon to combine. Pat the nut mixture evenly over the salmon fillets in the pan.
Bake the salmon for about 15 minutes or until the internal temperature registers 145℉ or the salmon is opaque inside and flakes easily with a fork.
Notes
This recipe doubles or triples easily.To prevent overcooking, remove the pan from the oven when the salmon reaches 140ºF. Cover with foil and let it rest for a few minutes. The temperature will increase a bit more as it rests.If you use salted pistachios, you may wish to use less or no salt in the recipe.