Lanzhou is famous for its beef noodle soup Lanzhou niurou lamian. The noodles are always hand made, and the broth served hot and spicy with as much beef as you care to pay for.
Mazilu
Chain of restaurants specialising in Lanzhou niurou lamian
Other options:
UBC Coffee House
Zhongshan Road
Opposite Shengli Binguan
For when you need a Western food break thats consistent wherever you are.