Pork shoulder with balsamic caramelised apples

Ingredients

• 1.5 kg piece of pork shoulder, bone in
• 1 tbsp olive oil
• 2 onions, roughly chopped
• 2 tsp sea salt
• 4 Granny Smith apples (or allow half an apple per person)
• 4 tbsp balsamic vinegar
• 1 cup water, stock or white wine
• Small bunch of parsley, roughly chopped
• 1 tsp lemon zest