Wash the pumpkin, remove the seeds and peel the pumpkin. Cut into cubes and place on a baking sheet. Bake in the oven for about 35 minutes. Then let cool down a bit. Then puree finely in a bowl.
Finely crumble the shortbread and mix with the liquid butter. Line a 26-inch springform pan with baking paper on the bottom and press the crumbles onto it.
Mix the quark, sugar, pumpkin puree, eggs, vanilla pudding powder and lemon juice together. Spread the mixture on the crumbly base and smooth it out.
Bake in the preheated oven for approx. 55 to 60 minutes on the 2nd rack from the bottom. Then let cool down completely.
Mix the sour cream with agave syrup and brush the cake with it. Scatter pumpkin seeds on top.