Shish Kabob House is a nice hidden gem in this food category in Las Vegas. It's located fairly off the strip and in an uninteresting shopping center. But you walk in and the owners are great and the food delicious.
The prices are ridiculous as well, with most meals around $10 for portions large enough for 2 meals. The Shish kabob meal is your best bet. The hummus was probably average, and I was disappointed no tzatziki sauce was offered without a request, but still a worthwhile meal
I don't know about authentic, but the food was super tasty and filling. Probably the best Mediterranean, Lebanese, etc. cuisine that I've been to so far.