"Unsophisticated" is perhaps not the right word, but I'm hosting a friend later this month who loves good food, but not terribly complex and definitely not pretentious. Ethnic cuisine is fair game. Places I’m thinking she’ll like are Shake Shack, Ippudo, Katsu-Hama, Motorino, the Dutch, Shopsin’s. I might be underestimating my friend a bit; on the other hand, I’ve watched her order too much chicken at nice restaurants over the years :)
You should take her for the chicken sandwich at brunch at nomad!
Yakitori totto (midtown west) or yakitori taisho (e village), both have a wide selection so your friend will have less ambitious choices and you can order some of the more adventurous options.
Ukranian national home for pierogies and crepes:
Murray's cheese bar (their newer cafe) has some great cheesey food
Porchetta, Num Peng, Caracas Arepa, Walker's ( burgers), Blue Ribbon Chicken, Georgia's, Yokocho, Meatball Shoppe, Sole di Capri, Misoya ( ramen), Rockmeisha.