Steve's only heard a few vague details about how Natasha and Tony met. Something to do with her going undercover to get a read on him for SHIELD, but that alone makes it clear that they probably didn't get along too well at first either.

"Yeah, yeah," he says, waving her off as he tilts his head back and takes a decent swig of his drink. The alcohol still burns on the way down, causing him to wince briefly. "But you've gotta admit, I look pretty good for ninety-five."