Need great lunch place near 19th and K
You don't say what price point, but the Oval Room is close by. I haven't been to Kellari Tavern, but it is close too, as well as, Spezie. I haven't been to Spezie in over a year, it was very good when I went, but I would check for a more recent review.
Vidalia is also very close.
For something less expensive Mai Thai is decent and is where lots of people have business meetings in that area.
1200 19th St NW, Washington, DC
1736 L Street NW, Washington, DC 20036