Turn the broiler on high. Salmon should be placed skin side down on a baking sheet lined with foil.
Combine salt, mustard, and honey in a small bowl. Apply the mixture to the fish evenly.
Crush cashews with the back of a wooden spoon or the side of a chef's knife. Toss on top of the fish.
Depending on your broiler and the thickness of the fish, it may take 5–10 minutes to broil salmon until the thickest section readily flakes with a fork.