Preheat the oven to 350 degrees Fahrenheit with a rack in the middle position.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar on medium speed until the butter appears lighter in color, about 1-2 minutes.
Add the vanilla extract, and mix until combined.
Add eggs one at a time, mixing until combined after each egg is added.
Add the milk and sour cream. Mix to combine. If you can, cover the bowl of your mixer to prevent splashing.
In a medium bowl, whisk together the flour, salt, baking powder, and ground cinnamon. Add the dry mixture to the wet mixture in the mixer.
Mix on low speed until combined. Do not overmix.
Prepare a loaf pan by spraying it liberally with baking spray.
Pour the batter into the prepared loaf pan, and even out the top with a rubber spatula. Sprinkle the cinnamon sugar evenly over the top of the batter.
Bake for 40-45 minutes, or until a cake tester comes out clean.
Let cool in the pan for about 15 minutes, then remove the churro bread from the pan and place it on a wire cooling rack. Let cool to room temperature (or as long as you can ;) )
Enjoy!
