I always use Kosher salt in my kitchen! If using table salt, start with half the amount and adjust to taste, as it is much "saltier" by volume.
Instructions
Batter
Preheat the oven to 350°F. Line the bottom of a 9x5 loaf pan with parchment paper and heavily butter the sides of the pan to prevent sticking.
Cream butter and sugars in a large bowl until light and fluffy, about 3-4 minutes. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
Whisk together the flour, baking powder, and salt in a separate bowl.
Alternate adding the dry ingredients and buttermilk to the butter mixture, starting and ending with the dry ingredients. Mix until just combined.
In a small bowl whisk together the ½ cup of dark brown sugar and 1 tablespoon of cinnamon.
Pour half of the batter into the prepared pan. Sprinkle over all but 2 tablespoons of the cinnamon sugar mixture. Pour over the remaining half of the batter over the cinnamon sugar mixture and spread out evenly. Now sprinkle over the remaining 2 tablespoons of the cinnamon sugar. Using a knife make a swirl through the batter.
Bake for 55-60 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs.
Finishing Touches
Remove the bread from the oven and let cool in the pan for 5-6 minutes. Carefully lift the bread out of the pan, remove the parchment paper and place on a cooling rack to cool before icing.
Whisk together the powdered sugar, milk, and vanilla extract until smooth. Drizzle over the cooled bread. Enjoy!
Notes
Use a metal 9x5 loaf pan for the best results. Glass pans tend to cause uneven baking.
Using the dark brown sugar in the cinnamon sugar mixture adds a rich layer that enhances the flavor. Light brown sugar can be substituted.
Let the bread cool in the pan for about 5-6 minutes, then carefully remove it and transfer to a cooling rack (remove the parchment).