Preheat the oven to 210°C. Pat dry your chicken and place in a roasting tin. Place the garlic and half a lemon into the cavity of the chicken. Gently pull the skin away from the top of the chicken and place a handful of rosemary leaves underneath the skin along with a couple of slices of butter. Rub the rest of the butter into the skin of the chicken making sure to get it into all the nooks and crannies. Sprinkle salt all over the chicken, be generous.
Place the chicken into the oven and cook for 20 minutes. Then turn down the oven to 180°C and cook for another 70 minutes. Once the time is up make a cut into the chicken and make sure the juices run clear. Leave to rest for 10 minutes under a sheet of foil before carving.
Nutrition information is an estimate and will vary depending on the exact ingredients used.