In a large mixing bowl, combine the flour and salt. Make a well in the center and add the eggs, sour cream, vegetable oil, and lukewarm water.
Mix until a dough forms. Turn the dough out onto a lightly floured surface and knead for about 5-7 minutes until smooth and elastic.
Wrap the dough in plastic wrap and let it rest for at least 30 minutes.
On a lightly floured surface, roll out the dough to about 1/8 inch thickness.
Using a round cutter or a glass, cut out circles of dough about 3 inches in diameter.
Place a small spoonful of plum jam (Powidl) in the center of each dough circle.
Fold the dough over the filling to create a half-moon shape. Press the edges together firmly to seal. Use a fork to crimp the edges for a decorative finish.
Bring a large pot of salted water to a gentle boil. Carefully drop the dumplings into the water in batches.
Cook for about 5-7 minutes, or until the dumplings float to the surface. Remove the cooked dumplings with a slotted spoon and drain well.
In a large skillet, melt the butter over medium heat. Add the breadcrumbs and cook, stirring constantly, until golden brown.
Remove from heat and stir in the granulated sugar and ground cinnamon.
Gently toss the cooked dumplings in the breadcrumb mixture until well coated.
Arrange the Powidltascherl on a serving plate. Serve warm, optionally with a dusting of powdered sugar or a dollop of whipped cream.
Enjoy your meal!