Preheat oven to 350° (180° celcius). Grease and flour 2 x 8 or 9 inch (20-22cm) cake pans (springform or classic) or line with parchment paper.
On medium speed beat the eggs, yolk and sugar for approximately 2 minutes, add the milk, oil and vanilla, beat again for 1 minute. Add the flour, baking powder and salt, beat for 2 minutes.
Pour the batter into the prepared pans, bake for approximately 20 - 25 minutes (check with toothpick to make sure they are done, when 2 or 3 crumbs are stuck to the toothpick they are done). Let cool for about 15 minutes before removing from the pans and cool completely before filling with the Nutella.
On round serving dish place one of the cakes top down, spread with the Nutella*, then place the 2nd cake on top (top side up) and dust with powdered sugar. Enjoy!
*If the Nutella is too hard to spread then you can thin it out either by heating in a microwave or by heating with a bain marie.
Notes
For room temperature ingredient remove from the fridge 1-2 hours before using, depending on the warmth of your house.For storage, wrap the cake in plastic wrap and keep it at room temperature. It should keep for a couple of days.
The cake can also be frozen. Freeze tightly wrapped in plastic in an airtight freezer safe bag or container. Properly stored it will keep for up to six months in the freezer.