Stir together yeast and 1/3 cup water in a small bowl until yeast is dissolved, then let stand until foamy, about 5 minutes. (If mixture doesn't foam, discard and start over with new yeast.) With motor running, pour yeast mixture and remaining 1 1/3 cups warm water into flour mixture in processor, blending until dough forms a ball and pulls away from side of processor bowl, about 1 minute.