1. Boil the fillets in water, adding a little of the soy sauce or tamari to the water, for about 10 minutes.
2. Strain and let cool.
3. In a bowl, mix the tomato, the rest of the soy sauce or tamari and the barbecue spice.
4. Dip the fillets through this mixture, on both sides.
5. Place in air fryer at 200°C/390ºF for 10 minutes. Flip them over after 6 minutes.