Allow 1 x 1.4kg whole chicken to sit at room temperature for 30 minutes before roasting.
Preheat the oven to 190˚C/170˚C fan/gas mark 5. Halve 1 lemon and 1 onion and push inside the cavity of the chicken. Rub olive oil over the skin and season inside and out.
Place in a roasting tin and roast for 1 hour 20 minutes or until the chicken is completely cooked and the juices run clear when the thickest part of the thigh is pierced with a skewer. Transfer to a plate, tent loosely with foil and allow to rest until cool enough to carve.