Light charcoal grill or preheat oven to 425F
Place chicken breast-side down, with the legs towards you. Using kitchen scissors or shears cut along either side of the backbone to remove it, save the backbone for stock
Turn the bird breast side up and just press down with the palm of your hand to make it lay flat.
Make a shallow cut through the skin at the joint between the drumstick and thighs, to allow excess moisture to escape while roasting. And Make a shallow cut at the joint between the wings and breast
Mix the lemon zest, rosemary and butter together
Season inside and outside generously with salt, pepper, and brush with butter
You want a medium-hot grill, Pile the charcoal on one side of the grill, you don’t want the chicken to be directly over the flames.
Place the chicken on the grill skin side up with the legs closest to the flames, but again, not over the flames
Cover the grill and roast the chicken for 30-45 minutes, until and an instant-read thermometer inserted into the thickest part of the thigh meat, reads 165F
Let rest for about 5-10 minutes covered in aluminum foil.