Preheat and Prepare: Position an oven rack in the center and preheat your oven to 400°F (205°C). Line a large roasting pan with parchment paper for effortless cleanup.
Create the Spice Blend: In a small bowl, thoroughly combine the ground turmeric, cumin, coriander, smoked paprika, kosher salt, and the optional cayenne pepper.
Prep the Cauliflower: Wash and thoroughly dry the cauliflower. Trim the outer leaves and the base of the stem. Slice the head vertically through the core into ¾-inch thick "steaks." Separate any florets that break away from the main sections.
Oil the Cauliflower: Place all the cauliflower steaks and florets into a large mixing bowl. Drizzle with the olive oil and toss gently with your hands or tongs until every piece is lightly and evenly coated.
Season Generously: Sprinkle the prepared spice mixture over the oiled cauliflower. Toss again until the golden-hued spices are uniformly distributed, ensuring all surfaces are seasoned.
Arrange for Roasting: Transfer the seasoned cauliflower to the prepared roasting pan, arranging it in a single layer. Ensure there is space between the pieces to promote browning rather than steaming.
Roast to Perfection: Place the pan in the preheated oven and roast for 35 to 40 minutes, carefully flipping the pieces halfway through the cooking time. The cauliflower is done when it is fork-tender and showcases deep golden-brown, caramelized edges.
Garnish and Serve: Remove from the oven and transfer the roasted cauliflower to a serving platter. Scatter the fresh, chopped parsley over the top and serve immediately.
