Tomorrow Belongs To Me by valtyr: Steve wakes up in the 21st Century. He doesn't think much of it, and it's dubious about him. He meets a Norse God, joins a superhero team, and feels terribly awkward about the whole monument at Arlington he's rendered obsolete by not being dead. Meanwhile, Tony is trying to make his mark on history by being the man who finally drove Nick Fury over the edge.

The part you're thinking of is about a quarter of the way through:

"Are you a heterosexual, Steve?" Volstagg said, and they all leaned in with interest. "Jane and Tony assured us they both had more conventional tastes, but many Midgardians choose to limit themselves."