• Preheat oven to 350°F. Spray an 8 by 4-inch loaf pan with nonstick spray and line it with parchment paper to create a sling for removing bread later.

Make the Cinnamon Sugar Mixture

• Mix together the cinnamon and sugar in a small bowl and set aside.

Make the Batter

• In a large bowl, whisk together flour blend, baking soda, and salt; set aside.
• In a medium bowl, whisk together sugar and egg. Mixture will be thick. Add sour cream, oil, milk, and vanilla, and continue whisking until fully incorporated.
• Pour wet ingredients into dry ingredients and whisk until smooth.
• Pour half of the batter into prepared pan and sprinkle with most of the cinnamon/sugar mixture (hold back about 2 tablespoon for the top). Pour the rest of the batter on top of the cinnamon mixture and carefully spread it to the corners (it may be a little bit hard to do as the cinnamon/sugar will want to cling to it).
• Sprinkle the rest of the cinnamon sugar on top and take a knife and run it through the batter to create a swirl.
• Bake the loaf for 55-65 minutes, or until a skewer or toothpick inserted into the center comes out clean. Tent the loaf loosely with foil halfway through baking to prevent over browning, if necessary.
• Remove from the oven and allow the loaf to cool in the pan on a wire rack for one hour. Then remove the bread from the pan and let it cool completely directly on the wire rack. Optionally, whisk together the icing ingredients and drizzle icing over top of the loaf. Slice and serve. Cover any leftovers and serve within 3-4 days. For longer storage, freeze for up to 3 months.