Austin: Sunday Night Dining Options
I don't think most Austinites wake up until at least 8pm, so 9pm isn't really "late night". ;^)
(Sorry for the smart-a** answer).
Austin's a pretty casual town, so you might want to include what kind of atmosphere you're looking for...I think your options are casual, laid-back, or "stoned out of your gourd". There might be a few fine dining options out there as well, but when I'm in Austin I'm always in one of the first three places. :^)