In a medium bowl, whisk together the pineapple juice, soy sauce, Marsala wine, brown sugar, sesame oil, garlic, chili powder and red pepper flakes until the sugar is dissolved. Place the chicken drumettes in a 1-gallon size, re-sealable plastic bag. Add the pineapple liquid to the chicken and seal with as little air as possible in the bag. Allow the chicken to marinate for three hours in the refrigerator.Place an oven rack in the center of the oven. Preheat the oven to 450 degrees Fahrenheit. Line a baking sheet with foil and spray liberally with vegetable cooking spray. Remove the chicken from the marinade and arrange in a single layer on the prepared pan. Season the chicken with salt and bake for 30 to 35 minutes until the skin is caramelized and very dark in spots.Meanwhile, place the marinade in a small saucepan. Whisk in the arrowroot, or cornstarch if using, and bring the marinade to a boil (in order to kill bacteria). Reduce the heat to a low boil and cook until thick, about 5 minutes. Cool for 10 minutes.Using a pastry brush, brush some of the cooked marinade over the chicken or pour into a small bowl and serve on the side. Arrange the chicken on a platter, sprinkle with chopped cilantro and serve.