In a small baking tray or casserole dish that’s just big enough to fill in all the salmon pieces, pour over ⅓ cup of the teriyaki sauce and marinate the fish skin side up for 15-20 minutes.
Air fried the salmon:
Line the air fryer basket with a thin layer of parchment paper or an air fryer liner. Slightly drip off the marinade and place the fish, side skin down, in the basket and with some gap between the fillets. Discard the marinade.
Air fry at 400F for 7 to 9 minutes. The exact time will depend on the thickness of the fish and your appliance. Mine was done at 7 minutes for medium-rare and 8 minute for medium.
To thicken the teriyaki sauce, take ¼ cup of the sauce and add it to a small sauce pot. Bring it to a low simmer. Gradually and slowly sprinkle in 1/8 tsp xanthan gum while whisking at the same time to prevent clumps.
The fish will be nearly opaque when cut into, at 120F (49C) at the thickest part. You can peek into the thickest part with a sharp knife or fork. It should flake easily, but still has a little translucency in the center.
Transfer the fishes to a plater. Glaze the salmon with teriyaki sauce. Sprinkle with toasted sesame seeds, if using, and scallions. Remove the skin before serving. I recommend serving them warm.
In a nonstick 12-inch skillet over medium-high, heat the oil until shimmering.
Place the salmon flesh side down in the pan, then immediately reduce to medium. Cook, undisturbed, until golden brown, 4 to 6 minutes.
Using a wide metal spatula, carefully flip the fillets, then cover the pan and remove from the heat. Let stand until the thickest part of the fillets reach 120°F or are nearly opaque when cut into, about another 5 minutes for 1-inch-thick fillets or about 8 minutes if 1.25-1.5 inches thick.
About the salmon:
Select fillets that have the same thickness.
Set the cook time a little less time than you think until you become more used to the timing of your appliance. The fish gets cooked quickly in the fryer. 1 minute makes a difference. You can also open it while it’s cooking and pop it back in to make sure it’s not overdone.
The nutritional label did not take the 1/3 cup marinade into calculations because it's discarded. For the 1/4 cup teriyaki sauce, I assume you use coconut aminos, which has slightly higher net carb than gluten-free tamari.