Ka'ak al-Quds (כעך) is the Jerusalem sesame bread: a tall oblong ring, soft and slightly sweet inside, with a burnished crust crusted thickly in sesame seeds. Split and filled, it becomes a street sandwich whose whole character rests on the bread, the seeds, and a filling kept simple enough to let both show. The angle is the loaf itself. The ring is the event, fragrant with toasted sesame and pleasantly chewy, so the stuffing is chosen to complement it rather than compete, and a sandwich made with stale or under-seeded ka'ak fails before the filling is even considered.
The build starts with the bread and stays light. The dough is enriched and lightly sweetened, shaped into a long looped ring, washed and rolled heavily in sesame so the crust bakes deep gold and nutty, with an interior that stays soft and tender. Sold warm from carts and bakeries, it is split along its length and filled to order. The classic stuffing is za'atar, a paper twist of the herb-and-sumac blend with olive oil for dipping or rubbed straight into the warm crumb, sometimes with a wedge of soft white cheese, a hard-boiled egg, or a few falafel tucked in. The point is that each of these leans on the sesame and the gentle sweetness rather than masking them. Done right, the crust shatters lightly under the seeds, the inside is warm and pillowy, and the za'atar or cheese reads as a clean counterpoint to the bread. Done wrong, the ring is stale and leathery, thin on sesame so the defining flavor is missing, or overstuffed so the bread that is the whole reason for the sandwich gets lost under the filling.
It shifts mostly by the filling and how warm the bread is. Plain za'atar and oil keeps it closest to its essential form; cheese makes it richer and more of a meal; egg or falafel turns it into a fuller handheld lunch. The closely related forms are recognizable on their own terms: the flat round Levantine ka'ak, and the small hard sesame rings eaten as a dry snack rather than split and stuffed. Each deserves its own treatment rather than a line here. They all return to the same idea this one states most plainly, which is a sesame-crusted ring whose flavor and chew are strong enough that the sandwich is designed to frame the bread rather than bury it.