Remove the seeds from the pumpkin and cut into pieces of about 5 cm. Either boil in lightly salted water until soft or steam in a steamer insert until soft. Drain and let cool completely.
Meanwhile, weigh and mix the ingredients for the flour mixture. Melt the butter and let cool again. Finely puree the cooled pumpkin. Weigh out 200 g of it and add to the flour mixture. Add the liquid butter (it should only be lukewarm, not hot!), milk and apple cider vinegar and knead with the dough hook of a food processor to a smooth dough. Place in an airtight storage box and refrigerate overnight (or 6 hours). (For the impatient, the recipe will also work if you let the dough rise, covered, at room temperature for 2 hours. But it is worth letting the dough rise overnight).
The next day, melt the butter for the filling and let it cool a bit. Knead the dough vigorously again. On a work surface lightly dusted with rice flour, roll out into a rectangle (30 x 35 cm). Cut in half lengthwise. Mix sugar with cinnamon. Brush dough with butter. Sprinkle cinnamon mixture evenly on top. Roll up each of the two sheets of dough tightly from the longer side and intertwine. Fold ends down. Place in a baking dish lined with parchment paper. Using a sharp knife, make 2 cm deep cuts in the dough strands (see video). Cover and let rise for 2 hours.
Preheat oven to 180 degrees (top/ bottom heat). Bake the bread on the second rack from the bottom for 35- 40 minutes. If the surface becomes too brown, cover with a sheet of baking paper. Carefully lift out of the pan with the baking paper. Let cool completely on a cooling rack. Warm jelly slightly and stir until smooth. Pour jelly evenly over the bread.