Directions

1. Preheat your oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan or line it with parchment paper for easy removal.

2. In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until well combined. Set aside.

3. In a large mixing bowl, beat the softened unsalted butter and 944 Spiced Vanilla Sugar together using an electric mixer on medium speed until light and fluffy, about 2-3 minutes.

4. Add the eggs one at a time, mixing well after each addition. Then, mix in the vanilla extract until fully incorporated.

5. Gradually add the flour mixture to the butter mixture, alternating with the sour cream. Start and end with the flour mixture, mixing until just combined and smooth. Do not overmix.

6. In a separate small bowl, combine the brown sugar, cinnamon, and chopped walnuts (if using) to create the streusel topping.

7. Pour half of the batter into the prepared baking pan and spread it evenly. Sprinkle half of the streusel mixture over the batter. Pour the remaining batter on top and spread it evenly. Finish with the remaining streusel mixture on top.

8. Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean and the top is golden brown. The internal temperature should reach 200°F (93°C).

9. Remove from the oven and let the cake cool in the pan for about 10 minutes. Then transfer it to a wire rack to cool completely before slicing.