Prep the cauliflower: Remove the outer leaves and trim the stem so the head sits flat. Keep the core intact; it helps hold the slices together.
Slice into steaks: Stand the cauliflower upright and slice from top to bottom into 1 to 1 1/2-inch thick slabs. You’ll get about 2–3 solid “steaks” from the center; use remaining florets for snacking or roasting.
Preheat the air fryer: Set to 390°F (200°C) for 3–5 minutes. A hot basket promotes quick browning.
Mix the seasoning: In a small bowl, stir together olive oil, smoked paprika, garlic powder, onion powder, salt, pepper, and red pepper flakes if using. Zest half the lemon into the oil for bright flavor.
Brush generously: Pat the steaks dry. Brush both sides with the seasoned oil, getting into crevices. Use any extra on stray florets.
Air fry, first side: Arrange steaks in a single layer in the basket. Don’t overcrowd. Cook for 7–8 minutes.
Flip and finish: Carefully flip with a wide spatula. Air fry another 6–8 minutes, until the edges are deep golden-brown and the centers are tender when pierced.
Season and brighten: Squeeze fresh lemon juice over the hot steaks. Taste and add a pinch more salt if needed. Sprinkle with chopped parsley.
Serve: Enjoy as a main with grains and a sauce, or as a side next to your favorite protein.