Tony doesn't have to be coherent; in fact, it's telling that he's not stringing full sentences together. Just hearing his own name gasped out and moaned like that is more than enough for Steve. He's struck by a fit of sudden, aggressive affection; he wants to just hold onto this man and curl his body around him and hold on, rock and stroke him through the throes of pleasure he's hearing. Pin him down and cover him with his own body and shield him from within and without.

Something clicks--something which he will analyze later, when he can think more clearly--because he can hear and feel Tony's reaction when he tries to push against Steve's powerful grip and fails to budge it. He can sense that's a catalyst that's pushed him past the point of no return, and at the moment why that doesn't matter.

Steve gives a softer, lighter groan in return, swallowing around Tony with no sign of objecting to it. Rather, he lifts his eyes up again to look at the man's face as he comes, tapering off the intensity of his attention to draw the spasms out as long as he possibly can.