Preheat the oven to 350 degrees F. Grease and flour a 10-cup Bundt pan.
In a large mixing bowl, beat the butter and granulated sugar with an electric mixer until light and fluffy, about 3 minutes.
Add the eggs one at a time, beating well after each addition.
Mix in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, and baking powder.
Add the flour mixture to the butter mixture in three additions, alternating with the sour cream and beginning and ending with the flour mixture. Mix just until combined after each addition.
In a small bowl, stir together the granulated sugar and cinnamon for the filling.
Spread half of the batter into the prepared Bundt pan.
Sprinkle the cinnamon-sugar mixture evenly over the batter.
Spoon the remaining batter over the cinnamon layer and gently spread it into an even layer.
Bake for 40 to 50 minutes, or until a toothpick inserted near the center comes out clean or with a few moist crumbs attached.
Cool the cake in the pan for 10 minutes.
Carefully invert the cake onto a wire rack and allow it to cool completely.
In a small bowl, whisk together the powdered sugar and milk until smooth.
Drizzle the glaze over the cooled cake before serving.
Christina's Notes
Use room-temperature butter, eggs, and sour cream for the smoothest batter and best texture.Do not overmix the batter once the flour is added. Overmixing can make the cake dense instead of tender.Sour cream gives this coffee cake its signature moist texture and slight tangy flavor.Cottage cheese can be substituted for the sour cream if needed, but blend it first for a smoother texture.Check the cake at the 40-minute mark, especially if your oven runs hot. Overbaking can dry out the cake.Serve with coffee, tea, or a glass of cold milk for a classic coffee cake experience.Store covered at room temperature for up to 3 days or refrigerate for up to 5 days.Freeze individual slices or the whole cake, tightly wrapped, for up to 3 months. Thaw overnight at room temperature before serving.The cake can be baked 1 day ahead. Wait to add the glaze until just before serving for the freshest appearance.