1. Rinse beef and pat dry; slice crosswise into 1/8-inch-thick strips 2 1/2 inches long. In a bowl, mix beef, lemon juice, allspice, and 1/4 teaspoon pepper; let stand 10 minutes.
2. Meanwhile, rinse and core tomatoes; cut each in half lengthwise. Set halves, skin up, in a 10- by 15-inch baking pan. Broil about 4 inches from heat until richly browned, 6 to 9 minutes. Reduce oven temperature to 200°. Stack pocket breads and wrap in foil. Warm in oven with tomatoes until ready to serve, 5 to 10 minutes.
3. Set a 10- to 12-inch nonstick frying pan over high heat. When hot, add beef mixture; stir until meat is no longer pink, 4 to 5 minutes. With a slotted spoon, transfer beef to a wide bowl or platter. Boil juices until reduced to 1/4 cup, 2 to 4 minutes; pour over meat. Stir in salt to taste.
4. Arrange tomatoes beside beef. Sprinkle onion and parsley over meat. Serve pocket breads, pickles, and Sesame Yogurt Sauce alongside. To eat, spoon beef mixture, tomatoes, onion, and pickles into pocket bread halves. Add yogurt sauce to taste.