In a small bowl, mix together the dijon mustard, honey, lemon juice, salt, pepper, and garlic powder (if using any).
Coat the salmon with the mustard mixture on all sides using either a brush or your hands.
Place the salmon in an oven-safe dish or baking sheet that is either lined with parchment paper or greased with avocado oil.
Pulse the pistachio in a food processor a few times or crush them in a Ziplock bag using a rolling pin or the bottom of a saucepan into small pieces and chunks (don't crush them too much).
Evenly spread the pistachios on top of the salmon.
Bake the pistachio crusted salmon in the preheated oven for 9 – 12 minutes depending on the thickness of the salmon filets.