“When the butter melted, it was rendered useless”

“Rendered butter” is a process (rendering) that creates more concentrated butter. It is not related to the expression “to render (something) useless,” but there are puns.
 
“When the butter melted, it was rendered useless” was posted on the website Pun of the Day on October 5, 2009.
   
“Why is melted butter no good? It’s rendered useless” is a riddle that was printed in the books A Man Walks Into a Bar 3 (2010) and Crap Jokes: Wet Yourself Laughing with the Ultimate Joke Book (2018), both by Jonathan Swan.
   
       
Cook’s Info
RENDERED BUTTER
(...)
Now, Rendered Butter is more a generic term that includes concentrated butters, beurre cuisinier, or something between clarified butter and ghee, though most uses involve describing a product with a butterfat content over 85%.
     
Pun of the Day
Great One Liners of the Month - October 2009 - page 3
21. When the butter melted, it was rendered useless.
 
Twitter
Dr_Bob
@Dr_BobsEmporium
#pun October 5, 2009 - When the butter melted,...: When the butter melted, it was rendered useless.[Click t.. http://bit.ly/klMDM
5:56 AM · Oct 5, 2009·Twitter Web Client
   
Google Books
A Man Walks Into a Bar 3
By Jonathan Swan
London, UK: Ebury Books
2010
Pg. 158:
Why is melted butter no good? It’s rendered useless.
   
Facebook
Food Puns
· January 24, 2014 ·
When the butter melted, it was rendered useless…
 
Twitter
Donna Ann Brown
@DonnaBrownBooks
When the butter melted, it was rendered useless. #wordchoice
1:00 PM · Oct 6, 2014·erased3412752
 
Facebook
The Annoying Orange
· May 3, 2017 ·
When the butter melted, it was rendered useless. HAHAHA!!
 
Google Books
Crap Jokes:
Wet Yourself Laughing with the Ultimate Joke Book
By Jonathan Swan
London, UK: Random House
2018
Pg. ?:
Why is melted butter no good? It’s rendered useless.