Sour Cream Cinnamon Coffee Cake

For the cinnamon-walnut filling:
Preheat oven to 325°F. Toast walnuts on a baking sheet for 10 minutes, until deep golden brown and fragrant. Let them cool on the sheet, then combine with brown sugar and cinnamon. Set aside.

Reduce oven temperature to 300°F.

For the coffee cake:
In a small bowl, combine flour, baking soda and salt.

In a large bowl with the paddle attachment, cream sugar and butter until light and fluffy, about 2 minutes.
Add eggs, one at a time, mixing well after each. Add sour cream and vanilla and mix on low until well combined. Scrape the sides and bottom of the bowl to ensure everything is incorporated. Add dry ingredients mix on low until batter is just combined.

Thoroughly coat a 9- or 10-inch bundt pan with nonstick cooking spray or softened butter. Dust with almond flour or all-purpose flour. Tap out any excess flour.

Pour half of the batter into the prepared pan. Sprinkle half of the cinnamon-walnut filling evenly over the batter. Add remaining batter and use a spatula to spread it evenly. Sprinkle remaining cinnamon filling mixture on top, spreading evenly.

Bake for about 70 minutes, until a skewer comes out clean. Cool cake in the pan for 15 minutes. Don’t let it cool in the pan for much longer than this or the brown sugar might stick to the sides of the pan and make it difficult to release the cake. Put a cooling rack on top of the pan and invert the pan. The cake should release easily.

For the icing:
Once cake has cooled completely, make the icing. Whisk powdered sugar and cream until smooth. Add more cream or sugar as necessary, until you reach a pourable consistency. Mix in the cinnamon and vanilla. Drizzle icing over the cake.

The cake will keep well in an airtight container at room temperature for up to a week.