In a large bowl, combine the first seven ingredients; beat on low speed for 30 seconds. Beat on medium for 2 minutes. Transfer to two greased and floured 9-in. round baking pans.
Bake at 350° for 20-25 minutes or until a toothpick inserted near the middle comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a large bowl, beat butter until fluffy. Add the confectioners’ sugar, milk, cinnamon and vanilla; beat until smooth. Spread frosting between layers and over top and sides of cake. Sprinkle with cinnamon-sugar. Store in the refrigerator.