Ronaldo’s stoppage-time penalty canceled out Ante Rebic’s 62nd-minute opener for Milan, which will be without Zlatan Ibrahimović for the return fixture because of a suspension.
Milan defender Theo Hernández was sent off in the 71st following a second yellow card.
There was heightened excitement at San Siro as it was the first time Ibrahimović and Ronaldo had faced off against each other since 2015, when Paris Saint-Germain played Real Madrid.
Nearly 73,000 spectators were present — a record for an Italian Cup semifinal.
Ronaldo had barely a sight of