Beyonce's Butt In Concert -- Come To 'On the Run Tour,' See B's ASS!

Beyonce and Jay Z wasted a ton of money filming a full-length trailer promoting their On the Run Tour because all they had to say was ... BEYONCE SHOWS OFF HER BOOOOOOOTY!!!!

The couple kicked off their tour in Miami Wednesday night and the show-stopping moment was definitely when she performed the song "Naughty Girl" ... wearing a costume with the ass cut out.

This is the best video we've seen featuring Beyonce since ...