For the cauliflower: Preheat the oven to 450 degrees F.
Heat the butter and olive oil in a small saucepan over medium heat until the butter melts. Add the garlic and curry powder and cook until fragrant, about 1 minute.
Make a small foil ring wide enough to hold up the base of the cauliflower a little. Put the foil ring in a large saute pan and place the cauliflower on top. Season the cauliflower with salt and pepper. Pour all but 1/4 cup of the curry butter over the cauliflower. Roast the cauliflower for 10 minutes, then baste with some of the curry butter on the bottom of the pan. Continue to roast and baste until the cauliflower is tender, about 45 minutes.
Meanwhile, add the almonds and raisins to the remaining curry butter in the saucepan and cook over medium heat until the nuts are toasted and the raisins are plump, about 3 minutes. Stir in the lime juice.
Remove the cauliflower to a serving platter and drizzle with any remaining butter from the saute pan. Top with the nut, raisin and curry butter mixture and sprinkle with the lime zest.
For the yogurt-tahini sauce: Whisk together the yogurt, olive oil, tahini, dill, cumin, garlic and lemon juice in a medium bowl. Season with salt and pepper.
Drizzle the cauliflower with the yogurt-tahini sauce and garnish with the cilantro, mint and chiles.