Preheat the oven to 350°F.

Spray a 9x5-inch loaf pan liberally with nonstick cooking spray. Set aside.

Place the butter, sugar, and vanilla extract in a large mixing bowl. Using a hand mixer or a stand mixer fitted with a paddle attachment, cream the ingredients together on medium speed until pale and fluffy, 3-4 minutes, scraping down the sides of the bowl as needed. Add two of the eggs, beat for 20-30 seconds until mostly combined, then add the remaining egg and sour cream, continuing to beat until combined.

Sift the flour, baking powder, salt, and cinnamon into the bowl. Beat the mixture on low, scraping down the sides of the bowl as needed, until it becomes a smooth, thick batter.

Using a rubber spatula, scrape 1/3 of the batter into the prepared loaf pan. Drop half of the Nutella by spoonfuls over the batter. Gently swirl the Nutella with a butter knife. Repeat the process with another 1/3 of the batter and the remaining Nutella. Scrape the last 1/3 of the batter into the pan.

Bake the cake on middle rack of oven until a toothpick inserted in the center comes out clean, 60-75 minutes.

Check to see that cake is done. Remove from oven or add time as needed.

Allow the cake to cool in the pan for 15-20 minutes. To release, run a butter knife between the edge of the cake and the pan. Turn the cake out onto a large plate.

Allow the cake to cool for 1-2 hours before slicing and serving.