Combine 1 cup tomato and 1/4 teaspoon each cumin, salt, and black pepper; set aside. Combine turkey, 3 tablespoons cilantro, and 1/4 teaspoon each cumin, salt, and black pepper. Shape into 12 (1 1/2-inch) meatballs. Heat vegetable oil in a large nonstick skillet over medium-high heat. Brown meatballs. Divide among pita halves, and top each with 1 lettuce leaf, 1/4 cup tomato mixture, and 1 tablespoon yogurt.