Ronaldo, who won the Ballon d'Or in 2008 when at Manchester United, led Madrid to the league title last season and has scored in his past six successive El Clasicos.
That would set up the mouth-watering prospect of four El Clasicos in the space of little more than two weeks, with the clubs also due to meet in La Liga on Saturday 16 April and in the Spanish Cup final on Wednesday 20 April.