Preheat the air fryer to 390°F (200°C).
Wash and thoroughly dry the broccoli and cauliflower florets to ensure maximum crisping.
In a large mixing bowl, combine the florets, olive oil, garlic powder, onion powder, salt, and pepper.
Toss the ingredients until the vegetables are uniformly coated with the oil and spices.
Place the mixture in the air fryer basket in a single layer, ensuring the basket is not overcrowded.
Cook for 10 to 12 minutes, shaking the basket vigorously at the 6-minute mark to promote even browning.
Transfer to a serving dish and drizzle with lemon juice immediately while hot.