I'm from South India, my dad is from Madras (Chennai) and my mom from Bangalore. And when I crave SOUTH Indian food, most times it's hard to find because most restaurants are North Indian. Then add to that they're run by bangladeshis (nothing against them but they should just run delicious Bengali restos, but I digress).
Thanjai is authentic South Indian and even the owner is South Indian and he cares about his food deeply. So come enjoy the dosas and idlies and don't forget to order the indian coffee! (South Indians NEVER drink chai!!!)