Make the dough: In the bottom of the bowl of a stand mixer, whisk the yolks, whole egg, sugar, butter, buttermilk and 3/4 of the orange zest together. Add 2 cups of the flour along with the yeast and salt; stir until evenly moistened.
Switch to the dough hook and add the remaining 1 3/4 cups flour and let the dough hook knead the mixture on low speed for 5 to 7 minutes. The dough should be soft and moist, but not overly sticky. Scrape the dough into a large, lightly oiled bowl (I usually scrape my dough briefly onto the counter, oil the mixing bowl, and scrape the dough back into it) and cover it with plastic wrap. Let dough rise at room temperature until doubled, which will take between 2 and 2 1/2 hours.
Assemble the buns: Butter a 23×33-cm (9×13-inch) baking dish, a heavier ceramic or glass dish is ideal here. Turn the risen dough out onto a floured work surface and roll it into a rectangle that is 46 cm wide (the side nearest to you) and 30 or so long. Spread the dough with cherries chocolate preserve and scatters over, 20 cherries cut in half.
Roll the dough into a tight, 18-inch long spiral. Using a sharp knife, very gently saw the log into 1 1/2-inch sections; you should get 12. Arrange the buns evenly spread out in your baking dish. Cover with plastic wrap and refrigerate overnight, or up to 16 hours.
The next morning, bake the buns: Take your buns out of the fridge 30 minutes before you’d like to bake them, to allow them to warm up slightly. Heat your oven to 190 degrees (350 d). Bake your buns until they’re puffed and golden, approximately 30 minutes.
Transfer pan to a cooling rack and let cool slightly. Make the icing by whisking the orange juice and powdered sugar together. Spread a little on each bun, or drizzle it over the whole pan. Serve immediately.
Ιn the summer, you don't need more than 1 1/2 hour to double the dough. This time didn't left it in the refrigerator over night, baked as soon as I put them in the pan and were equally good.
Don't have a stand mixer? Stir the mixture together with a wooden spoon, then continue stirring and beating it about in a large bowl for several minutes, until it comes together. Turn the dough out onto a floured counter and knead it for another 5 minutes. It will stick; don't sweat it. Just scrape everything up and into the oiled bowl when it's time to let it rise.