||Preheat oven to 220°C for the vegetables. Place lamb on a baking tray and squeeze over the juice of half a lemon. Drizzle with 1 tablespoon of oil and season with salt and pepper. Cover loosely with foil and leave at room temperature for 30 minutes.
||Place pumpkin, capsicum and zucchini on two baking trays, drizzle with 1 tablespoon of oil and season with salt and pepper and toss to coat. Roast for 35-40 minutes until vegetables are golden and cooked through.
||Preheat a barbecue to 220°C and cook lamb over an indirect heat for 15 minutes, serving side down. Turn the lamb over and cook for another 10 minutes for medium, or until a thermometer reads 60-65°C. Cover loosely with foil and rest for 15 minutes.
||To make tahini dressing, whisk the tahini paste, lemon juice and water in a small bowl until the consistency of thickened cream. Season with salt and pepper to taste. Carve the lamb against the grain and serve with roasted vegetables, tahini dressing and a sprinkling of dukkah.
||Switch to make: BARBECUED TANDOORI LAMB: Marinate the lamb in 1 cup of yoghurt and 3-4 tablespoons of tandoori paste and place in the fridge overnight. Cook following the instructions in Step 3.