I just visited DC and it was definitely not a destination for food, but Old Ebbitt Grill was really good and there was a hole-in-the-wall place called Po Boy Jim that had one of the best poboys I’ve ever had. Other than an okay burger, I can’t remember any other meal we had. The area around the national mall is a total food desert as far as we could tell.
As our Capitol tour guide said, “DC is full of people from around the country so there’s no real ‘culture’ here. I can tell you where the chick-fil-a is though.”
@Moose I second Old Ebbitt Grill, had a great meal and the restaurant is beautiful. If suggested to try bar seating its worth it, same food and was entertained by the bartender through the meal, was very enjoyable.
If looking for a easy lunch around the White House I would suggest GCDC (http://grilledcheesedc.com/) . A block away and food was really tasty, well as long as you like melted cheese.
If a night person food seemed to dry up, was able to get pretty good pub fare late at Capital City Brewing Company (https://capcitybrew.com/menus/) . Nothing unique so wouldn’t put it on a must see list, but good to know a place can get good food late if a night person (or just lost track of time taking pictures around the national mall at night).