I don't remember much about this particular fic, but
I know it's Eames' POV and in it he expects Arthur to want rough sex or a one-time fling thing. But Arthur gets upset or embarrassed when he's pushed around a bit and tells Eames that's not who he is.
Then Eames changes his tune when he realizes his read was bad and they have romantic sex.
This is the only bit I remember; couldn't tell you if it's a long fic or short or any other details.
Hoping someone might recognize the scene though.
Edit: Found!
https://archiveofourown.org/works/246292?view_adult=true