Andhra Bhavan is by far my favorite when it comes to a quick lunch on a weekday and if you are looking for something spicy and filling, you do not have too many other options that can compete. To top it all, if you want to look out for operational excellence and efficiency, you don't need to go farther than Andhra Bhavan.
Located in the heart of Delhi, the restaurant at Andhra Bhavan (the state house of Andhra Pradesh) has food to die for. Authentic Andhra thali with a whole lot of additions in the form of egg preparations, mutton, and chicken curries, etc is all that this place has to offer. However, this is more than what you would want on any given day. Full to the brim on weekdays during lunch time, the very process of getting a seat is a marvel. The Captain is astonishing in the way he remembers the order in which people need to be seated and somehow (maybe he has eyes at the back of his head) knows when a table is getting vacant behind him as he faces the chaos of waiting guests in front of him.
Once you have your seat (a full table if you are lucky or else if you go in a smaller group, sharing it with some other people in traditional community seating), you will SOON be served your thali with 3 different curries, daal, sweet, curd, mini puris, rice, and the famous gunpowder. While you are having your fix, there will be servers running around shouting "currrrry", "riiiiice" and so on. You can also request addition of a drink or a side order of egg or meat along with your thali and relish the same till it is time for you to vacate your table for some other hungry soul.
Overall, this place ranks right up there when it comes to the food but if you are someone who likes to sit in a relaxed, air-conditioned (yes, you only get fans here) environment, order, and leisurely sample his/her food, this is not your kind of place. Go there if you are prepared!