Cut lettuces lengthwise through core into 1 1/2-in.-wide pieces. Rinse well and pat dry.
Set out all ingredients on a cutting board, including zaatar and green sauce for seasoning. Swirl hummus with a spoon, making indentations; spoon about 2 tbsp. green sauce into indentations, then swirl a little more.
*Look for simit at Turkish restaurants and Middle Eastern bakeries.
Make ahead: Up to 4 hours, everything except bread and zaatar chilled separately.