Marble cake with nutella

I modernized this nice simple cake a bit and I didn't regret it :-)

Preparation steps

Beat butter, sugar, vanilla and salt well. Then add one egg at a time, stirring constantly, and mix until combined. Add buttermilk and mix. Finally add the flour mixed with the baking powder and mix just enough to combine.
Pour half of the prepared mixture into a greased and floured baking tray measuring 40x26 cm.
Add nutella to the other half and mix.
Using a spoon, take out the dough with the nutella and arrange it over the yellow part. Use a breast stick to make sarees on the dough.
Bake in a preheated oven at 180 degrees for 35 - 40 minutes, depending on the oven. Check with a toothpick if it is baked.
Leave the stake to cool completely, sprinkle with powdered sugar and cut into cubes.