In a small bowl, combine miso paste, mirin, sugar
Mix and set aside
Line the air fryer basket with parchment paper. This is optional, but I like to do it so I don't have to clean the basket afterward.
Put salmon filet in air fryer basket
Pour miso sauce on top of salmon
Cook at 350F for 10 minutes
Check the salmon to make sure the sauce is not burning. If the sauce seems to be charring too much, place a sheet of parchment paper on top of the salmon. The sauce's high sugar content makes it prone to burning.
Cook for another 2-5 minutes. The total cooking time for a half-pound salmon is about 12 minutes, but this will depend on the thickness of the filet.
Garnish with green onion (optional)
Serve with rice and enjoy