Cauliflower has become the superstar of the vegetable world in recent years. Its mild flavor makes an excellent blank canvas for nearly any spice and herb. Here we toss cauliflower florets with harissa, a North African hot chili powder that toasts to perfection in the oven. To balance the heat, the cauliflower is served with labneh, a creamy, tangy soft cheese made from yogurt. The dish is finished with crispy green onions and pickled red onions for more bursts of fresh flavor.