Cinnamon Swirl Bundt Coffee Cake

Step 1
Preheat the oven to 400 degrees F (205 degrees C). Grease a 10-inch Bundt pan.

Step 2
Beat sugar and butter together in a large bowl with an electric mixer until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla.

Step 3
Whisk flour, baking soda, and baking powder together in a separate bowl; add flour mixture in 2 batches, alternating with sour cream, beating batter briefly after each addition. Fold in walnuts. Pour 1/2 of the batter into the prepared pan.

Step 4
Mix sugar and cinnamon together in a small bowl; sprinkle over batter in the pan. Drop remaining batter in heaping spoonfuls over filling, covering it as best you can.

Step 5
Bake in the preheated oven for 8 minutes. Lower heat to 350 degrees F (175 degrees C) and bake until a toothpick inserted into the center comes out clean, about 40 minutes more. Cool on a wire rack for 5 minutes. Invert carefully onto a serving plate or cooling rack. Let cool completely.