Pre-heat oven at 350℉.
In a large bowl, whisk softened unsalted butter with sugar. Then add eggs, sour cream and vanilla extract. Whisk to combine.
Next, add flour and baking soda. Whisk to combine.
In a small bowl, combine both ingredients in cinnamon mixture with a fork.
Grease the insides of a 12-cup bundt pan using cooking oil spray.
Add 1/3 of the cake mixture to the bottom of the bundt pan, then sprinkle it with 1/2 of the cinnamon mixture.
Repeat Step 6, then top it off with the last 1/3 of the cake mixture.
Bake for 55-60 minutes. Insert a toothpick into the bundt cake to check for doneness. If toothpick comes out clean, cake is done. Let cake rest for 20 minutes in the bundt pan.
Prepare icing by combining all the icing ingredients. Whisk to combine until there are no lumps.
Tap all over the outsides of the bundt pan with a spoon to loosen cake. Then place a cooling rack or plate on the mouth of the bundt pan. Flip bundt pan over (along with plate) to remove cake. Tap the bottom of the bundt pan with spoon if needed to get the cake out.
Let cake cool completely before applying icing.
Serve and enjoy!