Preparation

• Position a rack in the center of the oven and heat the oven to 450°F.
• On a large rimmed baking sheet, toss the cauliflower and garlic with 3 Tbs. of the oil, 3/4 tsp. salt, and a few grinds of black pepper. Arrange the florets flat side down in a single layer. Cover tightly with foil and transfer to the oven to steam for 10 minutes.
• Carefully remove the foil, rotate the baking sheet, and roast until the bottom side is nicely browned, 10 to 15 minutes. Flip the cauliflower and continue roasting until just tender and deeply browned, 10 to 12 minutes more.
• Meanwhile, heat the coriander and cumin in a small heavy-duty skillet over medium heat, shaking the pan, until the seeds are just fragrant and lightly toasted, 1 to 2 minutes. Cool completely. Transfer to a spice grinder, and grind medium fine.
• Heat the remaining 2 Tbs. oil in the same skillet over medium-low heat. Add the ginger and cook, stirring, until fragrant, about 1 minute. Remove from the heat and stir in the cumin, coriander, turmeric, and cayenne. Swirl in the lemon juice.
• Discard the garlic and transfer the cauliflower to a serving bowl. Add the spice mixture, and toss gently. Season to taste with salt, garnish with the cilantro, if using, and serve.