In a large mixing bowl, combine the ingredients for the cake. Beat on low speed for 30 seconds, then increase to medium speed for 2 minutes. Transfer the batter into two greased and floured 9-inch round baking pans.
Bake for 20 - 25 minutes or until a toothpick inserted near the center comes out clean. Allow the cakes to cool in the pans for about 10 minutes. Remove from pans and place on wire racks to cool completely.
In a large bowl, cream the butter until light and fluffy - about five minutes. Add the powdered sugar, milk, cinnamon, salt, and vanilla extract. Beat until smooth. Then, assemble the cake by spreading the frosting between the layers, over the top, and on the sides. Sprinkle the top and sides with the cinnamon-sugar.