Cut the cauliflower into even-sized florets, about 1 to 1.5 inches each. Pat them dry with paper towels.
In a large bowl, toss the florets with olive oil, smoked paprika, cumin, garlic powder, salt, and black pepper until well coated.
Preheat the air fryer to 400°F (200°C) for 3 minutes.
Arrange the cauliflower in a single layer in the air fryer basket. Cook at 400°F for 12 to 15 minutes, shaking the basket every 5 minutes, until the edges are deeply charred and caramelized.
Transfer to a serving plate, sprinkle with parmesan cheese, squeeze fresh lemon juice over the top, and garnish with chopped parsley. Serve immediately.