Remove seeds from chillies and finely chop. Peel garlic cloves and finely chop. Juice the lemons and lime. Combine olive oil, chilli, garlic, lemon juice and lime juice into a mixing bowl and stir until mixed into a marinade.
Thaw the turkey if necessary. Remove the turkey from the bag and pat the skin dry with a paper towel. Place the turkey in a marinading tray with the breast side facing down. Cover the turkey with the marinade and leave in the fridge overnight.
On the day of cooking, preheat conventional oven to 210°C. Remove the turkey from the marinading tray and place in a roasting rack pan with the breast side facing up. Peel the onion and place it inside the cavity of the turkey. Coat the turkey with the marinade using a basting brush. Place the turkey in the oven and cook for 20 minutes. After 20 minutes remove the pan from the oven and turn the oven down to 180°C. Cover the turkey with aluminium foil and wrap the foil around the sides of the roasting pan. Place the turkey back in the oven and cook for a further 3.5 – 4 hours. Remove the pan from the oven and baste the turkey with the juices from the pan every hour. Cooking times may vary depending on your oven, however we recommend using a meat thermometer to check that the turkey has reached at least 76°C in the thickest part of the leg. Set turkey aside for 20 minutes to rest before carving.