Preheat the air fryer: Set to 390°F (200°C) for 3 to 5 minutes. A hot basket helps the broccoli crisp fast.
Prep the broccoli: Rinse, dry well, and cut into evenly sized florets. Patting dry is key to getting that char.
Make the sauce: In a small bowl, whisk soy sauce, toasted sesame oil, garlic, ginger, honey, rice vinegar, and red pepper flakes.
Taste and adjust sweetness or heat.
Toss with oil first: In a large bowl, toss the broccoli with neutral oil, black pepper, and a small pinch of salt. This coats the florets so they roast instead of steam.
Air fry, part one: Add broccoli to the basket in a single layer (a little overlap is okay). Cook for 5 minutes.
Sauce and shake: Pull the basket out, drizzle about half the sauce over the broccoli, and toss or shake to coat.
Return to the air fryer and cook another 3 to 5 minutes, until edges are browned and crisp-tender inside.
Finish and garnish: Transfer to a bowl, pour over the remaining sauce, and toss. Sprinkle with sesame seeds and green onions.
Serve: Enjoy hot as a side, or spoon over rice or noodles for a simple bowl.