To prepare dressing, combine first 8 ingredients, stirring with a whisk.
To prepare salad, bring 2 cups water to a boil in a medium saucepan, and gradually stir in couscous, raisins, and turmeric. Remove from heat; cover and let stand 5 minutes. Fluff with a fork. Place couscous mixture in a large bowl. Add tomato and remaining ingredients. Drizzle with dressing; stir well to coat. Cover and chill at least 1 hour.