Pat the salmon dry with paper towels and check for pin bones. Rub each fillet lightly with the olive oil.
In a small bowl, combine brown sugar, paprika, garlic powder, dried thyme, kosher salt, black pepper, and lemon zest until evenly mixed.
Sprinkle and gently press the spice-sugar mix over the top and sides of the salmon (avoid the skin side so the sugar won’t scorch). Let the coated fillets rest for 5 minutes while you heat the air fryer; this helps the rub adhere and melt slightly.
Preheat the air fryer to 390°F. For easy release, line the basket with a piece of parchment trimmed to fit and perforated with a few holes, or lightly mist the basket with oil.
Set salmon in the basket skin-side down. Air-fry for 6–8 minutes, depending on thickness, until the edges turn opaque and the center is just shy of done.
Increase the temperature to 410°F and cook 1–2 minutes more to deepen the caramelized crust. Transfer to plates and rest 2 minutes before serving.