Laser cut from parchment paper, no less:
Radial slits around the middle let it bend upward over the folded aluminum joint around the pillar:
Ours claims to be a 10×4-½ inch pan, roughly the diameter at the top and the overall height. Your pan will surely be different: this one is, as the saying goes, old enough to know better.
The SVG image as a GitHub Gist:
Sorry, something went wrong. Reload?
Sorry, we cannot display this file.
Sorry, this file is invalid so it cannot be displayed.
Made in anticipation of the next time Mary bakes a special carrot cake with cream cheese frosting for my birthday …
The Smell of Molten Projects in the Morning 
I hope she bakes one for you before your next birthday. Too long to wait!
Did you cut only one?
For well and good reason, the Special Cake is at most an annual affair, so a single liner should suffice for quite a while.
Now that you mention it, however, I made two more Just In Case an urgent need occurs.