With meat scissors or a knife carefully remove the backbone by cutting up alongside the bone on either side.
Open up the chicken and pound flat with a meat mallet to distribute the breast meat more proportionally to the size of the thighs for even cooking.
Sprinkle both sides with salt and pepper.
Loosen the skin from the meat but do not remove.
Slice one lemon very thinly. Distribute the slices under the skin.
Prepare a charcoal grill with coals only on one side of the grill.
Place the chicken bone side down on the grill close to the coals but not over them. Cut remaining lemon in quarters. Squeeze one quarter over the chicken.
Make a tent with foil to cover the chicken loosely but have one end hanging over the chicken and the coals. This will allow heat to flow up under the foil and over the chicken.
Turn chicken one quarter turn every 15 minutes until all four side have faced the heat. Each time squeezing another quarter of lemon.
Turn chicken skin side down directly over the coals for the last 15 minutes to brown.