Preheat the oven to 180°C (approximately 350°F).
Grate the pumpkin finely. Beat the butter with the sugar until fluffy. Stir in the eggs one at a time until fluffy, then add the lemon zest, juice, cinnamon and cloves. Mix the flour with the baking powder and ground hazelnuts and stir into the batter, alternating with the milk.
Grease the wells of the muffin tin or line with paper baking cups.
Pour the batter into the muffin tin and bake in the preheated oven for 25 minutes.
Remove the muffins from the oven, let cool briefly in the tin, then turn out and allow to cool.
To serve, cut the muffins in half and spread with cream cheese and jam.