Preparation Pour 3 cups warm water into large bowl of heavy-duty stand mixer fitted with dough hook. Sprinkle yeast over; stir to blend. Mix in 1 cup semolina flour. Let stand until small bubbles begin to rise to surface of mixture, about 40 minutes. Mix salt into yeast mixture, then beat in remaining 4 cups semolina flour, 1 cup at a time. Mix in 3 tablespoons oil, then 1 cup unbleached flour (dough will be slightly sticky). Turn dough out onto floured work surface; knead in lemon peel, rosemary, and 1/2 cup unbleached flour. Knead until dough is smooth, elastic, and satiny, adding more unbleached flour by tablespoonfuls if dough is too sticky, about 10 minutes. Form dough into ball; return to same bowl. Cover bowl with plastic wrap, then kitchen towel. Let dough rise in warm draft-free area until doubled in volume, about 2 hours. Punch dough down. Turn dough out onto floured work surface and knead 5 minutes. Divide dough in half. Sprinkle 2 baking sheets lightly with semolina flour. Roll out each dough piece to 12x8-inch rectangle. Transfer 1 dough rectangle to each prepared baking sheet. Using sharp knife, cut several 3-inch-long slits in each dough rectangle, cutting through completely. Pull slits apart, creating large holes in dough. Cover dough with kitchen towels and let rise in warm draft-free area until dough is doubled in volume, about 40 minutes. Meanwhile, position 1 rack in bottom third and 1 rack in top third of oven and preheat to 425°F. Bake breads until puffed and golden brown, reversing baking sheets halfway through baking, about 30 minutes total. Transfer breads to racks; brush remaining 2 tablespoons oil over top of breads. Cool at least 10 minutes. (Can be made ahead. Cool completely. Wrap breads separately in foil, then enclose in resealable plastic bags and store at room temperature 1 day or freeze up to 2 weeks. If desired, rewarm thawed breads wrapped in foil in 350°F oven for 10 minutes.) Serve breads whole or cut into thick crosswise strips. *A coarsely ground durum wheat flour that is available at some supermarkets, specialty foods stores, and Italian markets.
Preparation Pour 3 cups warm water into large bowl of heavy-duty stand mixer fitted with dough hook. Sprinkle yeast over; stir to blend. Mix in 1 cup semolina flour. Let stand until small bubbles begin to rise to surface of mixture, about 40 minutes. Mix salt into yeast mixture, then beat in remaining 4 cups semolina flour, 1 cup at a time. Mix in 3 tablespoons oil, then 1 cup unbleached flour (dough will be slightly sticky). Turn dough out onto floured work surface; knead in lemon peel, rosemary, and 1/2 cup unbleached flour. Knead until dough is smooth, elastic, and satiny, adding more unbleached flour by tablespoonfuls if dough is too sticky, about 10 minutes. Form dough into ball; return to same bowl. Cover bowl with plastic wrap, then kitchen towel. Let dough rise in warm draft-free area until doubled in volume, about 2 hours. Punch dough down. Turn dough out onto floured work surface and knead 5 minutes. Divide dough in half. Sprinkle 2 baking sheets lightly with semolina flour. Roll out each dough piece to 12x8-inch rectangle. Transfer 1 dough rectangle to each prepared baking sheet. Using sharp knife, cut several 3-inch-long slits in each dough rectangle, cutting through completely. Pull slits apart, creating large holes in dough. Cover dough with kitchen towels and let rise in warm draft-free area until dough is doubled in volume, about 40 minutes. Meanwhile, position 1 rack in bottom third and 1 rack in top third of oven and preheat to 425°F. Bake breads until puffed and golden brown, reversing baking sheets halfway through baking, about 30 minutes total. Transfer breads to racks; brush remaining 2 tablespoons oil over top of breads. Cool at least 10 minutes. (Can be made ahead. Cool completely. Wrap breads separately in foil, then enclose in resealable plastic bags and store at room temperature 1 day or freeze up to 2 weeks. If desired, rewarm thawed breads wrapped in foil in 350°F oven for 10 minutes.) Serve breads whole or cut into thick crosswise strips. *A coarsely ground durum wheat flour that is available at some supermarkets, specialty foods stores, and Italian markets.