Preheat oven to 350 degrees. Grease with shortening and flour 2 8" round cake pans. Set aside.
Beat cake mix, pudding mix, milk, oil, eggs, cinnamon and vanilla in bowl of electric mixer on low speed just to moisten, scraping sides as needed. Beat on medium speed 2 minutes.
Divide the batter between the two prepared pans.
Bake 22-24 minutes or until toothpick inserted into cake comes out clean. Cool in pans for 10 minutes, then remove from pans and cool completely on a wire rack.
Make the Cinnamon Frosting:
Beat 1 cup butter in large bowl of an electric mixer (whisk attachment and medium speed) until light, fluffy and almost white in appearance.
Add 1 teaspoon vanilla. Mix until blended.
Add in 1 tablespoon cinnamon and 2 cups powdered sugar**. Beat until well blended.
Add 3 tablespoons of heavy cream and beat until light and fluffy, about 2-3 minutes. Add more powdered sugar to stiffen the buttercream, or more heavy cream to make it more spreadable, as you desire.
Assemble the Cake:
Place one cake layer on a cake plate.
Spread a thin layer of frosting over the top of the cake.
Place the second cake layer on top.
Frost the entire outside of the cake with the remaining frosting.
Dust the top of the cake with cinnamon and decorate with cinnamon sticks if desired.
**This frosting is not a very sweet frosting. It's buttery and rich rather than sweet. If you would like to have the frosting more sweet, simply add more powdered sugar until it tastes as you would like it to taste.The calories shown are based on the cake being cut into 15 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**