Ronaldo's scored the second of the game, beating Donnarumma from close range after Mario Mandzukic had opened the scoring, but the 'keeper was too star-struck following the game to speak.
"It was so exciting to meet Ronaldo, because I was always up against him in my PlayStation games," he said to 'Rai'.
"I didn't speak to him, as I was too embarrassed."
Lucky for the young shot stopper, Ronaldo will not feature for Portugal as they prepare to take on Italy in the Nations League on Saturday, otherwise it would be two close encounters in the space of a week.
Gonzalo Higuain was sent off late in the game against his former side for confronting the referee, but Donnarumma insists there is no lasting damage in the squad.
"We forgave him, he is a great guy and apologised to everyone. It was a very important game for him and the key is that he knows he made a mistake, so won't do it again. He even spoke to the referee and apologised to him too," he added.