Udupi Palace seems like one of the most authentic Indian restaurants in SF. You're served on metal trays, and the dosas are huge, thin, and legit. It's pretty small inside and has something of the kind of atmosphere you find in restaurants in south asia. I certainly wouldn't use the word tranquil to describe it, but I've never found it too loud to enjoy a meal.
This area is a bit hard to park in so leave yourself extra time if you're driving.Pros: Authentic, Tasty