It happened at Penn Steaks located on the 4500 block of Lancaster Avenue.
The suspect was caught on surveillance walking into the restaurant at 6 p.m.
After ordering 2 cans of beer, he pulled out a handgun and demanded cash from the register.
When the store clerk ran down into the basement, the gunman ran behind the counter and stole $600 from the cash register.
He fled east on Lancaster Avenue.
No injuries were reported.
The suspect is described as a black male, 40-50 years-old, 5'6" tall with a stocky build and black and gray goatee. He was wearing a black winter hat, black hooded sweatshirt and black pants.
Anyone with information on this robbery should call police at
VIDEO: Click here to watch the surveillance video