Real Zaragoza edged a step closer to Copa del Rey progress on Thursday, but Real Betis were held on their travels.
A meeting between two Primera Liga rivals in Levante was as close as predicted, with neither the hosts nor Real Zaragoza willing to give an inch.
It appeared as though the game would end goalless until a last-gasp effort from Carlos Aranda, against his former employers, saw Zaragoza claim a slender first leg lead.
He pounced in stoppage-time to break the deadlock, with Levante left with no time in which to offer a reply.
They will now need to win on the road in the return leg if they are to progress.
Real Betis could only muster a 1-1 draw at Las Palmas, but will feel they are in pole position to reach the next round.
Ruben Castro grabbed Betis' away goal on 67 minutes, with that effort looking like it would be the match winner.
Las Palmas were, however, able to give themselves hope five minutes from time when Macauley Christantus levelled matters.