A stoppage-time goal from Borja Iglesias saved Real Betis a 1-1 draw against Rio Vallecano in the second leg of Thursday's Copa del Rey semi-final and sent Betis into the final 3-2 on aggregate.
Betis dominated the match at the sold-out Benito Villamarin Stadium, but failed to score and Rayo kept his dream of reaching his first Spanish Cup final alive when Bebe scored with a superb free kick 10 minutes from time .
The Portuguese midfielder fired an unassailable 30-yard shot into the top corner and the match was set to go to extra time.
Two minutes into extra time, however, 40-year-old Joaquin produced a fine piece of skill near the left touchline and put Sergio Canales into space with one-on-one with Rio goalkeeper Luca Zidane.
The former Real Madrid midfielder pointed the ball towards the goal and Iglesias threw it into the net.
Betis will play Valencia in the final on 23 April at the La Cartuja Stadium in Seville.