Make the labneh the day before you want to serve the dish. Line a sieve with a piece of cheesecloth (or a new J Cloth), put the yogurt into it and set over a bowl in the fridge. The yogurt will drain over the next 24 hours, leaving you with a firmer a€˜cheese-like’ substance. Help it along by giving it a squeeze every few hours.
Heat the oven to 160C/fan 140C/gas 3. Halve the tomatoes and arrange in a single layer in a large shallow roasting tin (or 2 small ones). Mix 4 tbsp extra-virgin olive oil, the harissa and saffron together and pour over the top. Turn the tomatoes with your hands to make sure they are well coated. Sprinkle with sugar and season. Roast for about 45 minutes cut-side up, or until they are caramelised and slightly shrunken. Leave to cool a little.
Take the drained yogurt out of the cheesecloth and mix it with the garlic and a pinch of salt.
Carefully move the tomatoes (they are quite fragile and easily fall apart) to a serving platter, dotting nuggets of labneh among them as you go. Pour some of the cooking juices from the roasting tin over.
Scatter on the almonds then heat the saffron with the lemon juice. Add 5 tbsp extra-virgin oil and mix. Spoon over the dish and serve warm or at room temperature.