The Bavarians meet the current title holders in the first leg of their last-four clash on Wednesday, leading the Germany international to call on his teammates to come together to nullify the in-form striker's threat at the Allianz Arena.
"We can only stop Cristiano Ronaldo as a team," Boateng told Kicker.
"In front of goal, he's like a machine. You can't shut him out completely, he always gets his chances in a game, because of the lines he runs and his excellent timing.
"Real base their game around him and it's important we give him as little room as possible."
Bayern have already been crowned Bundesliga champions and are now hoping to claim their sixth Champions League title.