Heat the oven: Preheat to 450°F (230°C). Place a large baking sheet inside to warm.
A hot pan helps the cauliflower crisp.
Prep the cauliflower: Trim the leaves and core, then cut the head into medium florets. Aim for even sizes so they roast at the same rate.
Season: In a large bowl, toss florets with 2–3 tablespoons olive oil, 1 teaspoon ground cumin, 1 teaspoon smoked paprika, 1/2 teaspoon garlic powder, 1 teaspoon kosher salt, and several grinds of black pepper. Add a pinch of red pepper flakes if you like heat.
Roast: Carefully spread the cauliflower on the hot baking sheet in a single layer, cut sides down when possible.
Roast for 20–25 minutes, flipping once, until deeply golden and tender with crispy edges.
Toast the couscous (optional but great): While the cauliflower roasts, warm 1 tablespoon olive oil in a medium pot over medium heat. Add the couscous and stir for 1–2 minutes until lightly golden and fragrant.
Cook the couscous: Add 1 1/4 cups hot broth and a big pinch of salt. Stir once, bring to a simmer, then cover and remove from heat.
Let it steam for 5 minutes, then fluff with a fork.
Add flavor: Zest the lemon directly over the couscous, then squeeze in 1–2 tablespoons lemon juice. Fold in 1/4 cup chopped parsley, 2 tablespoons chopped mint, and the sliced scallions. Taste and adjust salt, pepper, and lemon.
Make the tahini drizzle: In a small bowl, whisk 3 tablespoons tahini with 1 tablespoon lemon juice, 1 tablespoon warm water, a pinch of salt, and a tiny drizzle of honey if you like.
Add more water, a teaspoon at a time, until pourable.
Assemble: Spoon the herbed couscous onto a platter or into bowls. Pile the hot roasted cauliflower on top. Drizzle with tahini sauce.
Finish: Sprinkle with chopped toasted almonds or pistachios and crumbled feta, if using.
Add a final squeeze of lemon and a pinch of red pepper flakes for a little kick.