Preheat the oven to 175°C. Lightly grease and flour a loaf pan. In a small bowl, lightly beat the eggs with the vanilla. In a medium bowl, whisk the 1 1/2 cups of flour with the baking powder and salt.
In a large bowl, using a mixer, cream the butter and sugar at medium-high speed utnil fluffy. With the mixer at medium-low speed, gradually beat in the egg mixture until well mixed. Gradually add the flour mixture beating at low speed between additions until just combined. Continue to beat for 30 seconds longer.
Spread 1/3 of the batter in the loaf pan, then spread half of the Nutella on top. Repeat with another third of the batter and the remaining Nutella. Top with the remaining batter. Lightly swirl the Nutella into the batter with a butter knife. Do not overmix.
Bake the cake for about 1 hour and 15 minutes, until a skewer inserted into the center comes out clean. let the cake cool in the pan for 15 minutes. Invert the cake onto a wire rack, turn it right side up and let cool completely, about 2 hours. Cut the cake into slices and serve. (just quietly I didn’t actually wait until the cake was cool and thought it would also make a great dessert).