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UFC bantamweight champ Dominick Cruz fired back at Cody "No Love" Garbrandt -- calling him "the CM Punk of the 135 pound division."

Garbrandt has been talking all sorts of smack lately -- and even went after Cruz's back tattoo ... saying the tribal look is lame and outdated.

So, Cruz joined the guys on the "TMZ Sports" TV show (weeknights on FS1) -- and promised Garbrandt that his mouth is writing checks his ass can't cash.

We tried to get Cruz to give Garbrandt props for dating Paige VanZant in the past -- but he simply responded, "I don't know what she was thinking."

Funny stuff.