Prawn, pea & tomato curry

INGREDIENTS

• 1 tbsp vegetable oil
• 2 onions , halved, each cut into 6 wedges
• 6 ripe tomatoes , each cut into 8 wedges
• large knob of fresh root ginger , chopped
• 6 garlic cloves , roughly chopped
• 3 tbsp curry paste (we used Patak's tikka masala paste)
• 400g shelled raw king prawns
• 250g frozen peas
• small bunch coriander , leaves chopped
• basmati rice or chapatis, to serve