Using a heavy knife, cut the backbone from the chicken; discard. Open the chicken and place on a large cutting board, skin-side up; flatten with the heel of your hand. Rub the salt, chili powder, and five-spice powder all over the chicken. Cover and refrigerate 8 hours or overnight. Preheat a gas grill to high; reduce heat to medium after 15 minutes. (If cooking over charcoal, allow the coals to burn until they are covered with gray ash.) Remove the grilling grate. Combine the brown sugar and tea in an aluminum pie plate and place it directly on the lava rocks of the grill (or coals). Replace the grate and put the chicken on it, skin-side up. Immediately cover the grill and cook 50 minutes without opening it. Flip the chicken and cook about 10 minutes, until the skin is crisp or an instant-read thermometer inserted into the thickest part of the thigh registers 170° F.
Rainy-Day Method: Roast the chicken in a 400° F oven for 40 minutes or until an instant-read thermometer inserted into the thickest part of the thigh registers 170° F.