Prepare cake: Cream butter and sugar until fluffy. Add sour cream and vanilla extract, then beat in egg whites. In a separate bowl, whisk together flour, cinnamon, baking powder, and salt. Gradually add dry ingredients to butter mixture, alternating with milk and water, beginning and ending with dry ingredients. Mix until just combined. Pour batter into prepared cake pans and bake according to directions.

Frosting: In a large bowl, whip together butter, shortening, powdered sugar, vanilla extract, cinnamon, and milk until creamy and smooth.

Assembly: Once cakes are cooled, spread frosting over each layer. Then, frost each layer with cinnamon frosting. Stack layers and finish with frosting on top and around sides. Optionally, pipe decorations on top.

Prep Time: 30 minutes | Cook Time: 25 minutes | Total Time: 55 minutes | Kcal: 450 kcal | Servings: 12 servings