Super AU. Snap reunion type vibe. Public(ish)
He had to go do something with Bucky and Sam and Bruce after the memorial for Tony. Something about the infinity stones, he wasn't paying that much attention honestly. He was just too glad to be back and be alive and Natasha... He'd missed her.
He pulled her aside as soon as he saw her at the memorial and sure, he shouldn't be half undressing her in Tony's home when they're all morose and upset about his sacrifice. But Steve really couldn't help himself. At least he had enough decency to tug her into one of the rooms and kick the door shut behind them. No need to let one of the kids see anything.
"God, I missed you," he said between kisses, hands gently running through her hair before attacking the buttons on her blouse.