Rinse chicken and pat dry with paper towels. Cut chicken crosswise into 1/2 inch wide strips. Chop onions, garlic, and ginger. Finely grate lemon peel. Combine cumin, nutmeg, turmeric, cinnamon, red pepper, and cloves in a small bowl.Heat the wok over medium heat until warm. Add spice mixture and stir fry to release aroma and toast lightly. Return spice mixture to bowl.Increase heat to high.Drizzle oil into the wok and heat for 30 seconds. Add onions, garlic, ginger, and lemon peel. Stir fry about 5 minutes or until lightly browned. Add chicken and spice mixture. Stir fry until chicken is no longer pink in the center and is coated with the spice mixture.Stir in the water, vinegar, sugar, and salt. Bring to a boil. Stir until half of the liquid evaporates and the mixture thickens slightly. Spoon chicken mixture over rice. Garnish, if desired.