Okay but honestly we don't talk enough about the moments right before the "you trust me? I do" scene. Let's take a look (GIFS ARE NOT MINE, THEY ARE THE AMAZING'S @stevedanvrs)
First we have Tony doing his best to quickly explain the situation and the idea he has just gotten and then he looks as Steve.
Steve's a bit ??? at first and then IMMIDIETLY gets it even though Tony really didn't do his best at explaining. Like look at his face. He came from "what" to "oh" in like a second.
Then Tony tilts his head as if wanting to say "come on, come on you get it, please agree on it".
And then Steve CONFIRMS he does get what Tony's talking about and asks futhermore, just to know for a fact that he and Tony are on the same page.
And of course they are and then we have Tony back at it again with puppy eyes and a look saying I KNOW THIS IS CRAZY, BUT LISTEN...
And then there's Steve, cleanching his jaw as if "I can't believe he's doing it again, my husband is back on this bs" but he asks still, clearly believing him.
The point is Steve and Tony didn't need any words to both know what the other is thinking about and if this isn't a soulmate thing then idk what to tell you...