Sangak

Sangak or nân-e sangak (Persian: نان سنگک) is a plain, rectangular or triangular Iranian whole wheat leavened flatbread. In Persian sangak means little stone. The bread is baked on a bed of small river stones in an oven. There are usually two varieties of this bread offered at Iranian bakeries: the generic one which has no toppings; and the more expensive variety which is traditionally topped with poppy seeds and these days with sesame seeds, and to less extent black cumin, caraway, cumin and even dried aromatic herbs. Sangak bread was traditionally the bread of the Persian army. It is mentioned for the first time in the 11th century. Each soldier carried a small quantity of pebbles which at camp were brought together to create the "sangak oven" that would bake the bread for the entire army. It was eaten with lamb kabab.

Source: Wikipedia