Season breasts with za’atar, smoked paprika, salt and pepper.
In a large skillet over medium heat, add oil and when it gets hot, add the chicken breasts, seasoned side down. Season the top with the same seasonings; za’atar, smoked paprika, sea salt and pepper.
Cook the meat until just golden brown before flipping and cooking the other side, about 6 minutes depending on the thickness.
Transfer them to a plate and set aside.
Add sliced onions and season with sea salt. Sauté for 2 minutes or until they start to soften. If needed, add a little more oil before adding garlic; sauté for 30 seconds.
Add chicken broth and freshly squeezed lemon juice. Stir and bring the mixture to a simmer.
Return the chicken back to the skillet including any accumulated juices and spoon sauce over.
Cover, reduce the heat to medium-low and simmer gently for 10 to 12 minutes or until the internal temperature reaches 165ºF.
Transfer breasts back to the plate and increase the heat to high. When it starts simmering vigorously, add cornstarch mixture and stir until it thickens.
Add green and black olives, stir well before returning the chicken breasts, flipping them to coat with the sauce. Serve immediately.