Remove the leaves and trim the stem end of the cauliflower, leaving the core intact. Using a large knife, cut the cauliflower from top to base into three 3/4-inch-thick “steaks.” Season each steak with salt and pepper on both sides. (Reserve any loose florets for another use.)
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Sear the cauliflower steaks until golden brown, about 2 minutes on each side. Gently transfer the steaks to a baking sheet.
Whisk together the remaining 1 tablespoon of olive oil, ginger, cumin, and turmeric. Brush or spoon the mixture onto the cauliflower steaks.
Roast in the oven until tender, about 15 minutes. Garnish with cilantro and serve.