1.
Combine salt and sugar in a large pot, add hot water to dissolve.
2.
Add cold water, a few cups at a time, mixing well.
3.
Place chicken in brine, ensuring meat is completely covered. Refrigerate at least 6 hours or overnight. Remove chicken from brine. Rinse and pat dry.
4.
Preheat oven to 425 degrees F (220 degrees C).
5.
Rub butter all over chicken, season with salt and pepper to taste.
6.
Quarter the onion and lemon, skin-on, and crush the garlic with the flat of a knife. Stuff inside chicken.
7.
Place chicken in a roasting pan breast-side DOWN and roast at 425 degrees F, about 25 to 30 minutes per pound. Flip chicken breast-side UP for last 1/4 of cooking time.
8.
Chicken is done when internal temperature reaches 185 degrees F. Tent with foil and let rest 5 to 10 minutes before carving.