Place ground cumin, coriander, salt, picked thyme and chopped garlic into a small mixing bowl and mix together well and set aside.
Rub the ghee (clarified butter) over the entire piece of lamb followed by the spice, garlic and thyme mix.
Place the lamb into a large dutch oven and pour approx 200gm of water into the base of the pot. Place the pot into a pre- heated oven combi setting 160 °C for 3 hours.
For the tomato pickle: Place sugar, water, cinnamon, star anise, fennel and vinegar into a small saucepan and place on the stovetop over high heat and bring to the boil.
Cut the green tomatoes into 1cm slices and season liberally with salt and place the tomatoes into a large container. Once the pickle liquid has boiled pour it over the tomatoes and set aside.
For the red tomatoes roughly dice them and place into a separate mixing bowl with finely sliced Spanish onion, toss and set aside.
For the sumac yoghurt: In a mixing bowl mix together yoghurt, mayonnaise, pinch of sumac, zest of 1 lemon, salt and pepper. Taste and adjust seasoning if required and set aside.
Once the lamb has cooked remove from the oven and set aside to rest.
Assemble the tomato salad by removing the green tomatoes from the pickle liquid and transfer to a large mixing bowl with the red tomatoes and onion and picked parsley leaves. Dress with extra virgin olive oil and toss well.
Place some pita bread in the oven to warm.
To serve: Place a large dollop of yoghurt on a large serving platter and the lamb along side. Shred the lamb slightly off the bone and scatter the tomato salad over the lamb. Serve with warm pita and encourage your guests to make their own pita with yoghurt, lamb and tomato salad.