Marinate the chicken: Pound the chicken breasts to 0.8-inch (2cm) at the thickest part. Be sure they are the same thickness to ensure even cooking.
In a large bowl, add the lemon juice, olive oil, salt, ground sumac, or replace with 2 tablespoons lemon zest, ground coriander, cayenne pepper, ground turmeric, freshly ground black pepper, ground cinnamon, minced garlic cloves, lemon zest, and whisk well.
Add the chicken, and use your clean hands to massage the marinade all around the chicken. Cover tightly with foil paper or plastic wrap.
Or, you could also add the chicken breasts into a large zipped lock bag. Seal the bag tightly (getting the air out before zipping it closed), and squish the marinade all around the chicken..
Place in the refrigerator to marinate for 24 hours. If you are pressed for time, marinate it for 30 minutes before cooking.
Bake the chicken: If marinating overnight, allow the chicken to sit out at room temperature for 30 minutes before cooking.
Preheat the oven to 425º. Place the chicken on a parchment lined baking sheet or in a casserole and bake until chicken is browned and crisp on the edges, for 16-18 minutes or until the internal temperature reaches 165°F.
For crispier chicken, turn on the broiler to high and broil it for 3 minutes (keep an eye on it).
Remove the chicken from the oven and loosely cover the baking dish for 5-10 minutes, so the chicken can continue cooking in its residual heat, and the juices in the meat can redistribute.
While the chicken cooks, prep the dressing, onions, and the salad.
Prepare the tahini dressing: Combine all the ingredients in a blender (you could make the whole thing by hand).
Puree until smooth, stopping to scrape down the sides of the blender as needed.
Taste and adjust the seasonings if needed.
If seems too thick, thin it out with a little water (add 1 tablespoon at a time until it gets to desired texture).
Prepare the marinated red onions: Combine all the ingredients in a blender (you could make the whole thing by hand).
Measure the olive oil in a glass measuring cup. Add the vinegar and oregano and mix until combined. Pour the mixture over the onions and press the onions down until submerged in the oil.
Cover and let stand at room temperature for at least 12 hours before serving. If it’s more than 12 hours, my kitchen is hot, so it goes right into the refrigerator.
Prep the salad: Arrange the greens on a platter (or plates).
Layer on the chicken and add on the tomatoes, sliced cucumbers and red onions. cucumbers and red onions. Drizzle with the tahini dressing and enjoy!