Preheat the oven to 350 degrees F (180 degrees C). Grease and flour a 9-inch (23 cm) cake pan.
Whisk together the flour and baking powder in a large bowl.
Whisk together the eggs, milk, and melted butter in another bowl.
Add the wet ingredients to the dry ingredients and mix until well combined.
Stir in the sugar and vanilla extract.
Pour the batter into the prepared cake pan and spread evenly.
Bake for 25-30 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Let the cake cool for a few minutes, then remove it from the pan and place it on a wire rack to cool completely.
To make the filling, simply spread the chocolate hazelnut evenly over the cake's top.
For the ganache, heat the heavy cream in a small saucepan over medium heat until it comes to a boil.
Remove from the heat and add the chopped chocolate. Let sit for a few minutes, then whisk until smooth.
Spread the ganache over the top of the cake, then let it sit before serving.
Enjoy!