It was a little moment of revelation, I remember, when I first combined roasted cauliflower and raw grated cauliflower in the same dish. So different from one another, but working so well combined. This is lovely as it is, served as part of a spread, or spooned alongside some roast chicken or lamb. Don't throw away the leaves of the cauliflower here. They're delicious to eat, roasted and crisp, or grated raw as you would the rest of the cauliflower. If you want to get ahead, roast the cauliflower up to 4-6 hours in advance. Keep at room temperature and then just combine with the remaining ingredients when ready to serve.
Coarsley grate a third of the cauliflower and set aside in a bowl. Break the remaining cauliflower into florets, roughly 1 1/4 inches/3cm wide, and add these to a separate bowl with cauliflower leaves, if you have any, and the onion. Toss everything together and 2 tablespoons oil and 1/4 teaspoon of salt, then spread out on a large parchment-lined baking sheet. Roast for about 20 minutes, until cooked through and golden brown. Remove from the oven and set aside to cool.
Once cool, put the roasted vegetables into a large bowl with the 3 tablespoons (50ml) oil, the grated cauliflower, and parsley, mint, tarragon, pomegranate seeds, pistachios, cumin, and lemon juice, along with 1/4 teaspoon salt. Toss gently, just to combine, then transfer to a platter and serve.