That almost earned a real grin, if Tony hadn't quickly allowed it to be overtaken by a tight-jawed scowl, the cake not nearly a distant enough memory to be truly funny. Never a distant enough memory, really. Despite all of the cruel retaliation that Tony might have deserved for his behaviour towards Steve over many years, Tony believed that the cake was undue torture; above and beyond anything he could have possibly inflicted on Steve. Tony was still patting his stomach apologetically for the trespass as he explained, “I used the same process to make a geotextile padding for road structures in high impact earthquake areas. It's similar to a spinneret. Like a shower head.” Because that was a much safer topic than even thinking about that cake any more. It had probably bonded to his stomach lining. He probably wouldn't ever properly digest anything ever again. Liquid diet, from then until alcohol poisoning.
Steve didn't really want to talk about geotextiles. Tony didn't even want to talk about geotextiles, unless someone was paying him by the hour. His hand slid from his stomach and down his thigh to flick his fingers from his bouncing knee, casting it all off. “Did I say 'Happy Birthday' yet-- I haven't even seen you today so I guess I couldn't have,” he redirected, finally looking over at Steve and meeting his eyes, only to put on his self-effacing grin and regroup with his gaze down in his lap again. “I was hoping to get to the kissing booth, but I thought I was going to get Alzheimers waiting in that line. I think there's still, like, six-- trillion girls over there hoping you'll come back.”