Scatter nigella seeds over the surface, using about 1/2 teaspoon per bread. Oil or moisten your hand again and flatten each mound until it's about 1/4-inch thick, roughly 7 to 8 inches long and 4 to 5 inches wide.

Put 3 dough mounds on each sheet, spacing them evenly. With oiled or moistened hands, take a clump of dough about the size of a tennis ball (one-sixth of the dough, weighing just under 6 ounces), and let it drop from your hands onto one of the lined baking sheets. Line two rimmed baking sheets with parchment paper. Place a rack in the bottom of the oven and another rack in the top third. Preheat the oven to 550° or to its highest setting. Stir it down, re-cover and let rise until doubled again, about 1 hour. Cover the bowl with plastic wrap and let rise until doubled, about 1 1/2 hours, depending on how warm your kitchen is. Stir in half the flour, the flax seed and the salt, then stir in the remaining flour and mix well. Put the water in a medium bowl, and sprinkle the yeast over the water, stirring with a fork to dissolve.

In Yemen, where Shuli Madmone's parents were raised, this flatbread would be baked on the sides of an outdoor oven resembling an Indian tandoori.

Whole wheat flat bread