For curd dough, cream the butter with the powdered sugar and eggs. Stir in the curd, grated lemon zest, salt and breadcrumbs with a wooden spoon.
Let the curd mixture rest in the refrigerator for 2 hours. Then divide the dough into about 12-15 pieces (depends on the size of the plums).
Flatten one piece at a time in your hand, place a plum on top, cover with the dough and form round dumplings, Heat salted water in a pot and let the plum dumplings steep for about 15 minutes over medium heat.
For the sugar crumbs, melt the butter in a pan , add the crumbs and granulated sugar and let it toast a bit. Roll the plum dumplings in the sugar crumbs, sprinkle with powdered sugar and serve.