Mix together eggs, sugars, salt, oil, pumpkin and baking spices until well combined.
After no lumps remain, add all-purpose flour and baking powder, mixing until just combined.
Spray baking pans with non-stick spray and evenly distribute batter into pans.
Bake at 350F for ~45 minutes until a toothpick comes out clean.
If baking ahead, the cakes can be removed from the pans, wrapped in plastic, and then placed in the freezer for easier handling when it's time to assemble. Do not assemble the cake until the cake layers have been fully cooled.
To make the whipped cream, add the heavy cream, salt and sugar to a mixer or mix by hand until stiff peaks are achieved.
Assemble the cake in the following order: 1st layer of cake, hazelnut spread, half of the toasted walnuts, half of the whipped cream, 2nd layer of cake, rest of the whipped cream, and rest of the walnuts