Ingredients

• 3 cups loosely packed fresh flat-leaf parsley leaves (from 2 bunches)
• 2 tablespoons cider vinegar
• 2 tablespoons water
• 1 tablespoon chopped shallot
• 1 teaspoon sugar
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• 1/4 cup olive oil
• 4 (6-inch) pita loaves with pockets
• 1/4 cup olive oil or vegetable oil
• 1 pound white onions, quartered lengthwise, then cut lengthwise into 1/4-inch-wide wedges
• 3/4 teaspoon ground coriander
• 1/2 teaspoon ground cumin
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• 1 pound sliced stir-fry beef (top round) or 1/3-inch-thick top round steaks, cut into 1/3-inch-wide strips

Instructions

1. Purée all sauce ingredients in a blender until smooth.
2. Make beef and onion pitas: Toast pitas on rack of a gas burner over high heat, turning with tongs, until heated through but still pliable (pitas may puff), about 1 minute, then wrap in foil to keep warm. (Alternatively, wrap untoasted pitas in foil and warm in a preheated 300°F oven or toaster oven.) Heat 1 tablespoon oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then sauté half of onions, stirring occasionally, until browned but still crisp, 4 to 5 minutes. Transfer to a large plate. Sauté remaining onions in 1 tablespoon oil in same manner and transfer to plate (reserve skillet). Stir together coriander, cumin, salt, and pepper in a bowl. Pat beef dry and toss with spices. Heat 1 tablespoon oil in skillet over moderately high heat, then sauté half of beef, stirring, until browned but still pink inside, 1 to 1 1/2 minutes. Transfer beef to plate with onions, then sauté remaining beef in remaining tablespoon oil in same manner.
3. Toast pitas on rack of a gas burner over high heat, turning with tongs, until heated through but still pliable (pitas may puff), about 1 minute, then wrap in foil to keep warm. (Alternatively, wrap untoasted pitas in foil and warm in a preheated 300°F oven or toaster oven.)
4. Heat 1 tablespoon oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then sauté half of onions, stirring occasionally, until browned but still crisp, 4 to 5 minutes. Transfer to a large plate. Sauté remaining onions in 1 tablespoon oil in same manner and transfer to plate (reserve skillet).
5. Stir together coriander, cumin, salt, and pepper in a bowl. Pat beef dry and toss with spices. Heat 1 tablespoon oil in skillet over moderately high heat, then sauté half of beef, stirring, until browned but still pink inside, 1 to 1 1/2 minutes. Transfer beef to plate with onions, then sauté remaining beef in remaining tablespoon oil in same manner.
6. To serve: Halve pitas and fill with beef and onions. Serve sauce on the side.
7. Halve pitas and fill with beef and onions. Serve sauce on the side.