1) Preheat the oven to 200C/Gas mark 6. Place the prawns in a baking tray and sprinkle with the salt and pepper. Pour the olive oil and lemon juice over the prawns and roast in the oven for 5 to 6 minutes.
2) For the dressing, place all the ingredients in a bowl and stir until blended. Serve the dressing with the roasted prawns.