Start making thin slices of red onions, sauté them in a pan with a little olive oil adding some salt.
When brown, sprinkle with balsamic vinegar, and let them simmer for fifteen minutes until softened.
Make thin slices of the pumpkin, steam for ten minutes.
Line a cake pan with parchment paper.
Place on top of the pastry the brown onions and the slices of pumpkin.
Bake for about ten minutes at 180° C.
Remove the cake from the oven, whisk the eggs with milk and salt and pour it on the cake along with some Gorgonzola cheese.
Bake for ten minutes at 180°C.
Garnish with hazelnut crumbles.