The 2-0 success against Espanyol meant new head coach Gabriel Calderon's first home match in charge was one to remember, and allowed Betis to see a glimmer of light through the relegation trap door.
Betis have looked doomed to the drop, having become increasingly marooned at the foot of the table while their winless stretch has continued.
They are still floundering eight points adrift of Almeria in 17th place, but Argentinian Calderon will see it as a start.
After four barren months, Betis needed something to cling to and star forward Ruben gave them it, netting in the 71st and 89th minutes.
Salva Sevilla headed an early chance wide from Joan Verdu's corner, and Ruben also missed the target in the formative stages of Sunday's tussle.
Juan Carlos saw a shot blocked by Espanyol midfielder David Lopez before Ruben cleared the bar from the edge of the penalty area.
Betis reached half-time knowing they had created sufficient chances to be ahead, but without taking one.
Ruben tried again to no avail early in the second half, and former Real Madrid reserve Juanfran also shot wide.
But the peppering of Espanyol's goal was rewarded with a breakthrough.
Lorenzo Reyes drilled a grass-skimming 25-yard strike that crashed against the left post, with the ball rebounding invitingly for Ruben to sidefoot into the net from 10 yards.
If that was a gift, Ruben's second goal was a treat for the home supporters at the Benito Villamarin stadium.
Leo Baptistao fed a long pass out to the striker on the left flank, from where he made a beeline for the penalty area, and as marker Abraham Gonzalez retreated Ruben cracked a powerful low shot into the left corner.