Roast cauliflower with lemon harissa sauce

From Nigel Slater in the Observer - https://www.theguardian.com/food/2021/dec/19/nigel-slater-recipes-for-roast-cauliflower-plus-festive-chocolate-treats

Serves 4

Ingredients

• cauliflower 2, small to medium ones
• onion 1, medium
• olive oil 3 tbsp
• garlic 3 cloves
• assorted tomatoes 800g
• harissa paste 1 tbsp
• lemon the zest of 1
• coriander and parsley 25g

Method

1. Preheat the oven to 200C/gas mark 6. Trim the cauliflowers to discard the thickest part of the stalk, taking care to leave the florets intact. Remove any tatty leaves. Put the cauliflowers in a roasting tin then pour in enough boiling water to come halfway up the cauliflowers. Cover tightly with foil and bake for 45 minutes. They are ready when soft enough to effortlessly take a metal skewer through the stalks of the florets.
2. Peel and thinly slice the onion. Warm the oil in a deep saucepan, then add the onions and cook for about 15 minutes until soft and turning golden. Peel and slice the garlic and add to the onions.
3. Roughly chop the tomatoes and add them to the onion, then continue cooking over a moderate heat for about 15 minutes, until soft and easily crushable. Season with salt and black pepper, then stir in the harissa paste and lemon zest. Remove the leaves from the herbs and chop finely, then stir into the sauce.
4. Remove the cauliflowers from the oven, drain thoroughly and serve with harissa and lemon sauce.