In a small saucepan, add a stick of butter and place over medium high heat
Stir and keep a close eye until little bits of golden butter form
Once the butter gets golden, remove it quickly and move it to a new container to cool and ensure it does not burn. Wait for the butter to become solid again before using in the icing (you can pop it in the freezer to speed up this process)
In the base of a kitchen aid or large bowl with a hand mixer, add cooled, browned butter and cream cheese
On medium high speed, beat the cream cheese and butter until fluffy (around 2 minutes)
Add salt, cinnamon, and vanilla. Whip until combined
On low speed, add the powder sugar ½ cup at a time
Once all the sugar has been added, turn up the mixture and whip on medium high until light and fluffy (around 2 minutes)
Spread icing over the cooled, sheet cake in an even layer. This is a generous amount of icing, so add as much or little as you like