Published: 2019-02-08 04:46:36 BdST
Kevin Gameiro grabbed a stoppage-time equaliser for Valencia after Denis Cheryshev had reduced the deficit with 20 minutes remaining, leaving the tie in the balance heading into the second leg at the Mestalla stadium on Feb. 28.
Betis striker Loren Moron headed Betis in front at the end of the first half and Joaquin doubled their advantage in bizarre circumstances early in the second.
The veteran midfielder whipped in a corner which crossed the line before Valencia's goalkeeper Jaume Domenech could pat it away, with the referee awarding the goal after consulting the Video Assistant Referee (VAR).
Betis, who last lifted the trophy in 2005, looked to be in pole position to reach the final in May, which will be played at their stadium, but Russia forward Cheryshev punctured the party atmosphere with a glanced header.
Cheryshev almost levelled in the closing stages with a second header but instead struck the crossbar, but French striker Gameiro completed the comeback with a strike in added time.
The fightback gives Valencia a huge psychological edge heading into the second leg, knowing that a goalless or a 1-1 draw will be enough for them to reach the final.
Barcelona drew 1-1 at home to Real Madrid in the first leg of the other semi-final tie on Wednesday.