Preheat the oven to 350 degrees. Spray a 12 cup capacity bundt pan with cooking spray containing flour. Set aside.
In a large bowl, whisk together the flour, sugar, brown sugar, baking soda, baking powder, cinnamon and salt.
Add the butter and use an electric mixer to beat the butter into the dry ingredients until you get a mixture that resembles coarse crumbs.
In a medium sized bowl, whisk the eggs. Add in the vanilla, milk and sour cream and whisk. Add the wet ingredients to the dry ingredients and mix until combined.
Once the batter is well mixed, remove about 2 ½ cups of the batter and set it aside.
In the original bowl, add in the brown sugar and cinnamon and mix until well combined.
Start by layering the batter with the plain one on the very bottom of the bundt pan. Spoon about half of the cinnamon layer over that, followed by the plain batter. Repeat until the batters are all in the pan, beginning and ending with the plain batter.
Place the pan in the oven and bake for 50-55 minutes, or until a knife comes out cleanly.
Allow the cake to rest in the pan for about 10 minutes after baking before turning the cake out onto a cooling rack to come to room temperature.
Once the cake is cooled, whisk the frosting by combining the powdered sugar, vanilla and start by adding 2 tablespoons of heavy cream, adding extra until reaching a consistency of thick frosting. Spoon the frosting on top of the cake. Slice and enjoy!
Store any leftovers in an airtight container for up to 3 days.