Preheat the oven to 400 degrees Fahrenheit.

In a small bowl combine the oregano, onion, garlic, parsley, rosemary, sugar, salt, pepper, cornstarch, and lemon zest to form a dry rub. Set aside.

With a large knife cut the chicken lengthwise into 2 halves. Start by removing the back bone by cutting down both sides of it (freeze the back bone to make stock from it in the future, optional). Then cut through the breast bone to separate the chicken into 2 halves.

Rub the chicken halves on both sides with some olive oil. Dredge the chicken halves in the dry rub from step number 2, making sure it is applied to all areas and crevices of the chicken.

Place the chicken, skin side up, on a rack on a baking pan. Bake in the oven for approximately 60 to 90 minutes until an instant read thermometer, in the thickest parts of the chicken thighs, reads 170 degrees Fahrenheit. Tent with aluminum foil at approximately the 40 to 45 minute mark to keep the skin from getting too dark.

Remove from the oven and immediately squeeze the half lemon over both halves of the chicken. Let sit 10 minutes before carving.