Bruce/Tony
To be fair, Tony wasn't sure anyone really considered him to be exceptionally open, so it wasn't like Bruce was particularly in the minority. Hell, he wasn't even overly friendly most of the time, not by most people's standards anyway. There was just entirely too much sarcasm for that.
Still, once he was done dusting himself off, Tony peered into the offered bag before snatching up a donut for himself. "Bruce, right," he agreed, and his smile was charming enough, he thought. "I found some pumpkin tarts. Good stuff. I might have to just go back and buy the whole company. But oh, hey, these are good too." Billionaires were allowed to talk with their mouths full.