In a wide pan, warm the olive oil, then add the onion with a pinch of salt and fry until soft. Add the garlic and spices and fry for a minute or two until fragrant, then add the tomato purée. Cook out the purée for a couple of minutes, stirring to make sure it doesn’t catch on the bottom of the pan. Pour in the tinned tomatoes, then rinse out each tin with a splash of water and pour that in too. Break up the tomatoes with a wooden spoon and simmer for about 10–15 minutes to thicken the sauce.

Quarter and deseed the preserved lemons, then chop them into small pieces before adding to the sauce. I would recommend adding the lemon a tablespoon at a time, tasting as you go to find the right balance. I say this because they come in many sizes and strengths, so you really need to taste and get the amount right for you.

To make the tahini sauce, grate the garlic into a bowl, squeeze over the juice of half a lemon, mix and leave for 5 minutes. The acidity of the lemon will relax the heat of the garlic. Pour in the tahini and whisk together – it will begin to stiffen – then slowly pour in the ice-cold water, a tablespoon at a time, whisking as you go until you have a smooth, drizzly sauce. You want it to be quite runny.

Season with a pinch of salt and a dash of cumin. Taste and adjust with a little more salt and/or lemon as need be. Season the fish and nestle it into the tomato sauce.

Cook for about 5–10 minutes, depending on the thickness of the fillets, until just cooked. Serve immediately, with warm pitta and couscous, and finish with lots of tahini sauce and fresh coriander