Preheat the oven to 180 degrees circulating air or 200 degrees top / bottom heat.
Clean and peel the pumpkin and cut the pulp into approx. 3 mm thin slices. Pluck the thyme leaves from the stems. Mix the goat cream cheese and sour cream in a bowl until smooth and season with 1 teaspoon salt and pepper to taste.
Roll out the puff pastry together with the baking paper on a baking sheet. Fold around a small edge and press down lightly. Spread the goat cheese cream evenly on the dough. Spread the pumpkin slices on top. For the non-vegetarian version, cut 100 g Serrano ham into small pieces and spread on the quiche. Bake the quiche on the middle rack for about 30 minutes until golden brown.
Meanwhile, roast the pumpkin seeds in a pan without oil for about 2 minutes. Then take it out and let it cool down. Peel the onion, cut in half and cut into thin strips.
Heat 2 tablespoons of oil in the pan you used previously and sweat the onions over medium heat for about 3 minutes until light brown. Sprinkle 1 teaspoon of sugar over the top, stir in the thyme leaves and simmer for about 10 minutes over medium heat. Stir occasionally.
Take the golden-brown baked quiche out of the oven, cut in half and distribute the caramelized onions evenly on the quiche halves.
Arrange the butternut squash quiche on a flat wooden board or plate and garnish with the roasted pumpkin seeds.