You might try the Red Onion Cafe. It may have the best food.
One place I have on my list to try is Cafe on the Route in Baxter Springs.
If you wanted a couple of places that are truly Joplin ---
Fred and Reds-all they have is chile, tamales and hamburgers. My favorite is tamale deluxe. You eat it with crackers, which come heated. The seating is very limited though.
Undercliff Bar and Grill
Red Onion Cafe
203 E 4th St, Joplin, MO 64801