In a stand mixer with the paddle attachment beat the butter on a low speed. Slowly add the powdered sugar on batches until all the sugar is incorporated. Now beat on medium speed until light and fluffy for 5 -7 minutes.
Add cinnamon, vanilla extract and heavy cream, beat for 2-3 minutes until everything is well combined and the buttercream turns smooth and fluffy.
Transfer the buttercream to a piping bag to frost cookies, cupcakes, cakes, etc.,