You can use either sweet or sour cherries for this filling. Add a bit more sugar if using sour cherries as they are (obviously) not as sweet.
Put poppy seeds through a coffee grinder or food processor to grind them.
Sprinkle ground poppy seeds over the dough, then powered sugar. Place canned cherries over half of the dough. Dribble with melted butter, roll, and proceed with recipe above.