There are a few places in Newark on my "need to try" list, but as I've not yet been to any of them, please consider the following as leads rather than recommendations. They also might be at the edge of walking distance for a lunch break:
The Priory. Soul food and jazz. NOTE: They may no longer serve dinner/lunch.
233 W Market St, Newark NJ
Je's Restaurant. Southern, barbeque, soul food.
260 Halsey St, Newark, NJ 07102
27 Mix. Southwestern, asian, and italian fusion.
27 Halsey St, Newark, NJ 07102
Then there's McGovern's Tavern, where I haven't been since college days, but they served a decent burger and other bar food:
Good luck, and please let us know what you find!
All good suggestions. Je's has been around for years and is frequented by all the Newark movers and shakers. The Priory used to be one of my go to places when I worked in that area. Food was always very good. I've heard a lot of good things about 27 Mix but I have not personally had the opportunity to dine there. McGovern's is an interesting place, but not one that I would be recommending for lunch, unless it is a liquid lunch.