Pat the chicken very dry. Use paper towels to blot all sides, especially the skin.
Dry skin equals crisp skin. If you have time, leave the thighs uncovered in the fridge for 30–60 minutes to air-dry further.
Season generously. In a small bowl, mix 1.5–2 teaspoons kosher salt, 2 teaspoons black pepper, 1 teaspoon garlic powder, 1/2 teaspoon onion powder, and 1/2 teaspoon smoked paprika. Zest one lemon and add the zest to the mix.
Rub 1–2 teaspoons oil over the thighs, then coat evenly with the seasoning blend. Press it on so it sticks.
Preheat the air fryer to 400°F (200°C). A hot basket helps the skin crisp from the start. Preheating usually takes 3–5 minutes.
Arrange the thighs skin-side down in the basket. Leave a little space between pieces for airflow.
If your air fryer is small, cook in batches for best results.
Cook for 10 minutes. This jump-starts rendering the fat under the skin without scorching the seasoning.
Flip skin-side up and cook 8–12 more minutes. Aim for an internal temperature of 175–185°F for thighs. Higher than 165°F is fine here—dark meat stays juicy and becomes more tender. The skin should look deeply golden and crisp.
Add fresh lemon. Immediately after cooking, squeeze about 1 tablespoon of lemon juice over the thighs and sprinkle with a little more cracked pepper.
Rest 3–5 minutes so the juices settle.
Garnish and serve. Slice the remaining lemon into wedges for the table. Finish with chopped parsley or chives for a fresh pop of color.