Combine the yeast and sugar with a little of the warm water, and set aside until mixture is frothy. Sift the flour and salt into a large bowl, and make a well in the center. Add the yeast mixture, along with the remaining warm water. Using your hands, work the mixture into a dough, adding more water if necessary. Transfer dough to a lightly floured surface and knead until pliable and springy, about 5 minutes. Place dough in an oiled bowl, turning to coat, cover with a damp cloth and let rise in a warm place until dough doubles in size, about 1 hour.
Punch down risen dough and knead on a lightly floured surface. Roll into a log and cut into 2 to 3 equal pieces. Roll each piece into a ball, place on floured surface and let rest 30 minutes under a towel.
Preheat oven to 450 degrees F, and preheat baking sheets, tiles, or a baking stone.
Prepare the filling: Melt the butter in a skillet, add the onion and saute until softened, 5 to 7 minutes. Add the garlic and saute another minute. Transfer onion mixture to a large bowl, add remaining ingredients, and mix thoroughly with your fingertips. If mixture seems too dry, add a teaspoon of water.
Place a ball of dough on a floured surface and roll into a round, flat circle, about 1/8-inch thick. Place the round on the oiled, preheated baking sheets or tiles. Brush the top with olive oil and spread with a thin, even layer of the meat filling, leaving a 1/2-inch border around the edge. Repeat with remaining dough and filling.
Bake for 12 to 15 minutes. The dough should still be soft enough to roll up.
Squeeze a little lemon juice over each of the hot lahmacuns, and serve immediately either flat or rolled up into cones.
For the alternative filling: Mix all the filling ingredients in a bowl and blend thoroughly. Spread a thin layer on each circle of dough. Proceed with recipe, but bake for only 6 to 8 minutes.
c.1997, M.S. Milliken & S. Feniger, all rights reserved