Ronaldo hat trick puts Madrid into Champions League semis
Vidal appeared to mainly get the ball in his challenge on Asensio, although he could have received a second yellow earlier for a foul on Casemiro.
After Robert Lewandowski had scored a 53rd minute penalty for Bayern, an own-goal by Madrid defender Sergio Ramos in the 78th had given the German side a 2-1 lead in regulation time, and sent the game into extra time.
The victory at the Santiago Bernabeu Stadium put Madrid into the semifinals for the seventh straight season and kept alive its hopes of becoming the first team to retain the Champions League title since the competition's new format was created in 1992.
Madrid defeated city rival Atletico Madrid in the final both in 2014 and 2016.