Heat oven to 200C
Remove chicken from the fridge at least 20 minutes before starting to cook it
Cut the lemons in half
Put 1/2 a lemon and an onion in the bottom end of the chicken and 1/2 a lemon in the other end
Prick the chicken all over and squeeze another 1/2 lemon over the bird
Rub the bird with butter or oil and grate over some zest
Season with salt and pepper
Sit the bird on a trivet of vegetables ( onion , celery , carrot ) put the remaining lemon in the pan
Roast for 25 minutes per 500g plus another 25 minutes
Remove from the oven and allow to rest before carving . Squeeze any remaining juice from roasted lemons over the chicken before carving
Can be frozen . Could also be slow cooked for 4-6 hours