Preheat oven to 350 degrees F. In a large skillet, cook chicken and onion until chicken is no longer pink; stir to break up pieces. Drain off fat, if necessary. Add coriander, cumin, and 1 teaspoon salt; cook and stir for 1 to 2 minutes. Add undrained tomatoes, potato, plums, and olives. Bring to boiling; reduce heat. Simmer, covered, 12 to 15 minutes or until potatoes are tender. Uncover; cook 5 minutes more or until most of the liquid has evaporated. Wrap tortillas in foil; bake for 15 minutes or until heated. To assemble, place 1/3 cup chicken mixture in center of each tortilla; top with cheese. Sprinkle with additional chopped onion and snipped fresh cilantro. Fold tortillas in half. Makes 12 tacos (4 servings).