01 - Preheat the oven to 425°F and line a large baking sheet with parchment paper.
02 - In a large mixing bowl, whisk together olive oil, turmeric, cumin, coriander, smoked paprika, sea salt, and black pepper until well blended.
03 - Add cauliflower florets and sliced red onion, if using, to the bowl; toss thoroughly to ensure even coating with the spiced oil.
04 - Spread the coated vegetables in a single layer on the prepared baking sheet.
05 - Roast in the preheated oven for 20 to 25 minutes, stirring once halfway through, until the cauliflower is golden brown and tender with crisp edges.
06 - Transfer the roasted cauliflower to a serving platter, garnish with chopped fresh herbs, and serve alongside lemon wedges.