Add the cauliflower to a large bowl and cover with the coconut milk. Stir in the first amount of lime juice, the lime zest, the salt, chili powder, cumin and garlic powder. Cover and let sit for 30 minutes.
Meanwhile, preheat the oven to 450°F. When cauliflower has marinated for 30 minutes, drain the liquid and reserve.
Drizzle a baking sheet with the olive oil and add the cauliflower. Roast for about 40 minutes, flipping halfway through, until golden brown and tender. Let cool and break the cauliflower into small florets.
Meanwhile, measure 2 cups reserved coconut milk mixture and add to a small saucepan. Add turmeric (if using). Bring to a boil, then add quinoa and reduce heat to a simmer. Cover and cook for about 15 minutes, or until the quinoa is tender and all the liquid has been absorbed. Let quinoa sit for 5 minutes, then fluff with a fork.
While the quinoa is cooking, make the tahini drizzle. Add the tahini and second amount of lime juice to the remaining reserved coconut milk mixture and whisk until smooth.
When ready to serve, reheat the corn tortillas in a dry skillet, or directly over a gas burner until warm and pliable. Add a scoop of quinoa to each tortilla and top with cilantro, cabbage, carrots, and cauliflower. Drizzle with tahini mixture, additional fresh lime juice and hot sauce, if desired.
This nutritional information refers to each serving of the entire recipe and not just the products used as ingredients.