Make Natasha MacAller's roast lamb with turmeric and cumin

Ingredients

• 3 large onions (350g), unpeeled, sliced into rounds
• 3 large carrots (225g), peeled and cut into 5cm rounds
• 3kg lamb shoulder, bone in, lightly trimmed of fat
• 2 tbsp coriander seeds
• 2 tbsp cumin seeds
• 2 tbsp black peppercorns
• 1 tsp cardamom seeds
•  3 bay leaves, torn
• 1tsp ground turmeric
• 6 garlic cloves
• 2 tbsp salt flakes
• 2 tbsp olive oil
• 8 thyme sprigs
• 3 quince (or tart, firm apples), peeled, cored and cut into sixths
• 3 tbsp brown sugar
• 3 tbsp rice wine vinegar