Ground sumac and za’atar seasonings are available at Middle Eastern markets. Sumac (also spelled sumaq or summag) is made from the red sumac berry and has a lemony taste. Za’atar is a mixture of dried thyme and cilantro, sesame seed, sumac, and salt. There are different versions that you can buy or make.
Slice an onion thinly and sauté in a couple of tablespoons of olive oil with a few spoonfuls of sumac, za’atar, and 1 teaspoon of salt until soft.
While onions are cooking, chop 6 garlic cloves and stuff them between the skin and breast meat. Sprinkle salt on the top of the chicken and use your hands to spread garlic infused olive oil over the skin. Sprinkle some za’atar on your hands and rub it under the skin and inside the cavity.
Stuff the breast cavity with half a lemon and as many onions as will fit. Reserve the rest of the onions to serve with the roasted chicken. I can tell you from experience that if you over-stuff the chicken, the onions will fall out and burn!
Turn the chicken on its breast and salt and oil the back side. Roast the chicken breast down for an hour or until it is brown. Serve with the roasted and reserved sautéed onions.