For its size (small) Kanab has a lot of local restaurants and The Junction Drive-In appears to be one of the more popular. We have eaten lunch there several times and it is always busy. It is not uncommon to be standing in line to place your order.
We order the burgers, but are assured by the locals that other items on the menu (e.g., fish and chips) are equally good. The burgers are crispy on the edges and even though they are thin, they're made from good beef. The waffle fries are very good, crisp and fluffy at the same time. And the shakes are excellent. The food is prepared to order and even though there is a bit of a wait at the busy times, it is worth it.
You will probably pass by The Junction on your way through town. If you are at all hungry, it is worth a stop.