Preheat the oven to 180ºC (350ºF). Place the cauliflower head on a baking tray lined with baking paper.
Combine the saffron threads with 500 ml (17 fl oz/ 2 cups) boiling water and set aside to steep for 15–20 minutes.
In a bowl, combine the saffron liquid with the sumac, ground spices, oil and salt. Pour the mixture over the cauliflower, making sure it is evenly coated.
Cover the tray with foil and roast the cauliflower in the oven for 2 hours, basting every 30 minutes with the saffron liquid. Add more oil if needed to keep the cauliflower moist.
Remove the foil and roast for a further 10 minutes to brown the cauliflower a little.
While the cauliflower is browning, make the tomato salsa. Combine all the ingredients in a bowl and mix well. Season to taste with salt.
To serve, spread the tahini dip on a large platter and place the cauliflower on top. Cut out a generous wedge of cauliflower and pile the tomato salsa inside and around the edge of the cauliflower. Garnish with slivered pistachios, pomegranate seeds and chilli hair.
Note: Chilli hair is available from specialty food stores.
Recipes excerpted with permission from Feasting: A New Take On Jewish Cooking by Amanda Ruben, published by Hardie Grant Books March 2018.