For the dough, cut the pumpkin into slices and scrape out the seeds and fibers. Peel the pumpkin, dice it and simmer covered with about 100 ml water for 8-10 minutes until it is soft. Puree finely with a hand blender.
Measure out approx. 400 ml puree, let it cool down.
Grease a ring cake tin (approx. 24 cm Ø; approx. 3 l capacity) and dust with flour. Mix butter, 250 g sugar, vanilla sugar and 1 pinch of salt with the whisk of the mixer for 3-4 minutes until creamy.
Stir in the eggs one by one. Mix flour and baking powder and stir in alternately with the 400 g pumpkin puree briefly.
Spread the dough into the mould. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 50-60 minutes (stick test!). Let the cake cool down in the mould for approx. 20 minutes.
For the syrup squeeze oranges and lemons. Measure out a total of approx. 300 ml juice. Bring the juice and 150 g sugar to the boil and let it boil down open for about 10 minutes. Let cool down a little.
Turn the cake out of the tin and put it back into the tin. Prick the warm cake several times with a wooden skewer and sprinkle with the syrup. Let it cool completely. Serve with crème fraîche or sour cream.