ADD yeast to warm water; STIR; let set for five minutes.

In a large mixing bowl, COMBINE flour, sugar and salt; ADD yeast mixture and melted butter.

MIX for one minute to blend all ingredients; KNEAD for ten minutes until dough is soft, smooth and elastic, adding flour and water if needed to keep dough slightly tacky, but not sticky.

PLACE dough in a lightly greased bowl and TURN once to coat; COVER with plastic wrap and allow to rise at room temperature until doubled in volume, about 1 1/2 hours.

PUNCH the dough down; DIVIDE into four equal portions; ROLL into balls; COVER and let rest for 20 minutes.

PREHEAT oven to 450 F.

PLACE a baking stone or upside down baking sheet on oven rack to serve as a "hearth."

On a lightly floured surface, ROLL out each ball into a thin round, about 6 inches in diameter; let REST for a few minutes.

SPRAY the "hearth" with a mist of water; WAIT a few seconds; PLACE a dough round directly on the hearth.

BAKE until the dough puffs into a balloon, about three minutes; WAIT 30 seconds; REMOVE bread to a rack to coolNOTE: let oven reheat before doing the next pita (step 9.)