Instructions: Combine the yeast, 1 1/2 teaspoons flour, and sugar in the bowl of an electric mixer. Stir in 1/4 cup warm water, and let stand until creamy, about 10 minutes.

Whisk together the remaining 3 cups flour, cornmeal, rosemary, salt, and pepper; add to the yeast mixture. Using the dough hook, mix on low speed while slowly adding 1 cup warm water. Mix, adding warm water a tablespoon at a time if necessary, until the dough starts to pull away from the sides of the bowl. Mix until the dough is smooth and elastic, 5 to 6 minutes.

Turn out the dough onto a clean work surface, and knead four turns into a ball. Oil a large bowl, and place the dough inside. Cover the dough with plastic wrap, and let dough rise in a warm place until doubled, about 1 hour.

Turn out onto a clean work surface; divide into 12 smaller balls, each about two inches in diameter. Transfer the balls to a parchment-lined baking sheet, and loosely cover them with more plastic wrap. Heat oven to 400 degrees.

On a lightly floured surface, shape one of the balls into a 3- by 5-inch rectangle with your hands. Roll out the dough to a very thin 4- by 11-inch rectangle, and transfer to an ungreased baking sheet. Slice the onion lengthwise as thinly as possible, leaving the root end intact. Fan out each slice of onion. Brush the surface of the dough with olive oil; place 3 or 4 sage leaves, 2 slices onion, 2 slices tomatillo, and 2 slices tomato on top. Sprinkle with salt and pepper. Repeat with another ball of dough.

Transfer the baking sheet to oven, and bake until flatbread turns golden brown, 12 to 14 minutes. Transfer to a wire rack to cool. Working in batches, roll out, top, and bake remaining dough. Store in an airtight container up to 1 week.

Makes 12.

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