From Storyboard artist Lamar Abrams:

oh no! looks like vegeta gave the chaos emeralds to steven after all. but wait! didn’t yu-gi-oh blow up the moon? how is steven able to transform with no moon power?! find out on STEVEN’S LION! the next exciting episode of STEVEN UNIVERSE! boarded by Aleth Romanillos and Lamar Abrams (that’s me)!

STEVEN’S LION airs tonight at 8 PM on Cartoon Network!!