Prep the sprouts: Rinse, trim the stem ends, and remove any yellowed outer leaves. Halve lengthwise. If your sprouts are very large, quarter them so they cook evenly.
Optional quick soak for tenderness: Place halved sprouts in a bowl of hot tap water for 5 minutes, then drain and pat very dry. This helps soften the core without overcooking the edges.
Season: In a large bowl, toss sprouts with oil, salt, pepper, and garlic powder until evenly coated. Add lemon zest if using.
Preheat the air fryer: Set to 375°F (190°C) for 3 minutes. A hot basket gives better browning.
Arrange in the basket: Place sprouts cut-side down in a single layer. Do not overcrowd. Work in batches if needed.
Air fry: Cook at 375°F (190°C) for 10 to 12 minutes total, shaking the basket or stirring at the 6-minute mark. For extra char, bump to 390°F (200°C) for the last 2 minutes.
Finish: Transfer to a bowl. Toss with lemon juice and, if you like, a light drizzle of honey or maple syrup. Adjust salt and pepper. Add red pepper flakes or smoked paprika if desired.
Serve right away: They’re best hot and crispy. If making multiple batches, keep finished sprouts on a sheet pan in a 200°F (95°C) oven to stay crisp.