Dissolve the yeast and 1 tablespoon of sugar in the milk, cover and let rest for 15 minutes. Mix the salt, egg, half the flour and 75 grams (approximately 1/3 cup) of sugar with the yeast milk and the melted butter. Knead in the remaining flour gradually. Cover the dough and allow to rise for about 50 minutes.
Preheat the oven to 200°C (approximately 400°F)
Rinse the plums, cut in halve and remove pits. Knead the dough again, then roll out on a greased baking sheet, forming a raised border around the edges. Arrange the plums like roof tiles over the dough. Bake the tart in a preheated oven for about 45 minutes. Dust the finished tart with powdered sugar and serve warm or cold, with whipped cream if desired.