Remove the pits from the sour cherries. Sprinkle them with the sugar and leave them for about 30 min. to release their juice.
Sprinkle with sugar. Roll the 2 ends toward the middle and wrap into a roll. Arrange them in a suitable oven dish with a nonstick bottom that you've smeared with butter.
Bake in a moderately heated oven until golden. While still warm, pour the juice from the sour cherries over the fruit phyllo pastry. Sprinkle with powdered sugar and let it cool.