Step 1

Preheat the oven to 350°F. Line the bottom of 3 (8- inch) cake pans with parchment paper and grease the sides. (I used nonstick spray).

Step 2

In the bowl of your stand mixer fitted with the paddle attachment cream the butter and sugar together on medium speed until light and fluffy, 3-4 minutes. Add the sour cream and vanilla and mix until combined. Add 3 of the egg whites and mix until well combined. Add the remaining 3 egg whites and mix until well combined. Scrape down the sides of the bowl as needed to make sure everything is combined.

Step 3

Whisk together the flour, baking powder, cinnamon, and salt in a medium bowl. In a small bowl combine the milk and water. With the mixer on low speed add half of the flour mixture to the batter and mix until combined. Add the milk mixture to the batter and mix until combined. Add the remaining flour and mix until smooth, scraping the sides of the bowl as necessary.

Step 4

Divide the batter evenly among the 3 cake pans. Bake for 23-25 minutes or until a toothpick inserted in the center of the cakes comes out clean.

Step 5

Allow the cakes to cool 2-3 minutes in the pan and then remove them from the pans onto a wire rack to cool completely.

Step 6

In the bowl of your stand mixer fitted with the paddle attachment beat the butter and shortening together on medium speed until smooth. Slowly add in 6 cups of the powdered sugar and mix until smooth. Add in the vanilla, cinnamon and water or milk and mix until smooth. Slowly add the remaining 6 cups of powdered sugar and mix until smooth, scraping the sides of the bowl as necessary.

Step 7

In a small bowl whisk together powdered sugar, brown sugar, cinnamon, and water until smooth. Set aside.

Step 8

Use a large serrated knife to carefully remove any domes the cake formed when baking, so they’re flat. Place the first cake on a serving plate. Spread 2 1/2 tablespoons of the glaze over the cake layer. All it to soak into the cake. Spread 1 cup of frosting onto the top of the cake. Repeat the process with the second layer of the cake, and then add the final layer of cake and frost as desired.