In a bowl, mix the yeast with a bit of sugar, 2 tablespoons of sifted flour, 4 tablespoons of warm milk, and work into a thick batter - the yeast mixture, let it rise in a warm place. To the remaining flour, add sugar, egg yolks, lemon zest, melted butter, the rest of the warm milk, the risen yeast mixture, and salt. Knead into a soft dough. Let it rise in a combi steamer at 38°C in combined mode for about 20 minutes. When the dough has risen, roll it out to a thickness of about 15mm, and cut out donuts using a round cutter (glass). Use all-purpose flour on the work surface. Spray a Teflon baking sheet (Vision bake) with Rama Combi Profi, place the donuts on it, and let them rise again. Make a dent in each donut with a spoon and spray the top with Rama Combi Profi. Place in a preheated oven. After baking, spread with crushed plum jam, sprinkle with grated quark, add a dollop of cream, and dust with powdered sugar.