- 1 1/2 cups flour
- 1/2 tsp baking powder
- 1/4 tsp baking soda
- 1/2 tsp salt
- 6 Tbsp unsalted butter, at room temperature
- 3/4 cup sugar
- 1 large egg, at room temperature
- 2 tsp vanilla extract
- 1/2 cup plain fat-free Greek yogurt, at room temperature
- 1/2 cup low-fat buttermilk, at room temperature
- 1/3 cup Nutella
- 3 Tbsp unsalted butter, at room temperature
- 1/4 cup Nutella
- pinch of salt
- 1/4 cup powdered sugar, sifted
- 1 Tbsp heavy cream
- Preheat oven to 350°F and spray a 9 x 5-inch loaf pan generously with nonstick spray; dust pan lightly with flour.
- For the cake, whisk together flour, baking powder, baking soda, and salt in a medium bowl. Beat butter and sugar in a large mixer bowl at medium speed until light and fluffy; beat in egg and vanilla. Combine yogurt and buttermilk in a small bowl. Reduce speed to low and add half of flour mixture, beating just to combine. Add yogurt mixture, then finish with remaining flour mixture.
- Spoon half the batter into prepared baking pan and smooth with an offset spatula; tap pan sharply. Dollop spoonfuls of Nutella over the batter, gently swirling with a toothpick or wooden skewer. Spoon remaining batter into pan and smooth with an offset spatula; tap pan sharply to remove air bubbles.
- Bake for 48 to 52 minutes, until edges are golden, cake springs back to the touch, and a toothpick inserted in the center comes out clean or with a few crumbs attached. Cool in pan on a wire rack for 15 minutes; carefully remove cake from pan and cool completely on wire rack.
- For the frosting, combine butter, Nutella, and salt in a mixer bowl; beat on medium-high speed until smooth. Reduce speed to low and mix in powdered sugar and heavy cream until combined. Increase speed to medium-high and beat for 1 to 2 minutes, until light and fluffy. Use an offset spatula to spread frosting over cake. Chill for 30 minutes to set frosting before slicing and serving.