Slow-roast Persian lamb with pomegranate salad

INGREDIENTS

• 4 tbsp pomegranate molasses
• 1 tsp ground cumin
• juice 1 lemon
• 1 tbsp olive oil
• 2 garlic cloves , minced
• 1 onion , roughly chopped
• 1 shoulder of lamb , weighing about 1.6kg, lightly scored
• seeds 2 pomegranates
• handful flat-leaf parsley leaves
• 100g bag watercress
• 1 small red onion , finely diced
• flatbreads , to serve