1 Combine the water, salt and sugar in a medium saucepan and heat gently until the sugar and salt dissolve. Let the brine cool completely and then add a cup of ice to further chill the mix. Add the prawns to the brine and let them soak for 30 minutes (any longer and they’ll be too salty) before cooking.
2 Meanwhile, combine the tomato sauce, lemon juice, horseradish and chilli sauce. Taste and adjust the spiciness to your preference.
3 Preheat a barbecue (or grill pan) on high. Drain the prawns and dry them thoroughly with paper towels. Season them with the spice mix and add them to the barbecue along with the halved lemons. Cook the prawns until the shells are lightly browned and the meat just turns pink; about two minutes on each side. Cook the lemons until grate marks appear. To serve, set out the prawns and grilled lemons on a platter with the cocktail sauce alongside. Place an empty bowl on the table for the shells.500kJ per serve