There's not a huge food scene in Sofia, but we found some pretty good spots for Bulgarian traditional food and other good foods.
Benitza: pastry with sweet or savory filling Mekitsi (or mekitsa): fried dough
Meat-heavy cuisine--lamb, pork, beef, and horse are all common
Russian, Greek, Turkish, and Italian influences found in Bulgarian food
Restaurants
For traditional Bulgarian food, this was the only one we really loved. The service was friendly and all of the food was delicious. We had the 6 traditional Bulgarian appetizers plate, roasted lamb with rice and chopped pieces of lamb liver, sausage, lamb pastry, and polenta.
This cafe serves brunch, lunch and sweets. Their coffee was GOOD and they have a choice of chemex , french press (what we got), filtered, and a bunch more. They have nice lemonades both commercial and made in-house; we tried the elderflower lemonade and it was the right sweetness.
For brunch foods, they are a great place to try mekitsi. Theirs comes with 2 pieces of fried bread, a slice of mild feta, and blueberry jam. We also ordered scr
ambled eggs with sausage (very good), a poached egg dish served on yogurt (good taste but the cold yogurt cooled the eggs so this wasn't something I'd order again), a pork sandwich, french toast with eggs, cheese, and bacon, and many other yummy breakfast things, both traditional and new wave. We tried one of their cakes: cassis cream inside of a chocolate ball. It was very good. There are two locations. The one we went to is at ul. "Veslets" 10, 1000 Sofia Center, Sofia and is very close to several museums and churches which are probably on your sightseeing list.
Sweet treat, or just to look: We couldn't help but marvel at Hans and Gretel candy shop. You can buy binned candy--some you will recognize and others, like tennis ball gum, novel. They have sorbets and some over-the-top treats like donuts you can add decor to and hollow cakes that are filled with a customizable mix of syrups and ice cream. Outside they have giant mushrooms, a model of Gretel and a witch; it's a fun photo op location.
We went to Russian Restaurant Arabat which had pretty good Russian food and a nice view of the Russian church, and Pappous for decent Greek food.
For Bulgarian, we also tried some other highly-rated places too, without a ton of luck. Hadjidraganov's Cellar had really cute traditional decor and an extensive menu. A pork and chicken dish Dan got was good, the lamb stew I got was very oily and thus too rich, and we also had a sausage dish with a decent sausage but sides that were too plain. Mulled wine was a little bitter. Shtastliveca, which gets good google reviews, was terrible. The meat in the dish I ordered tasted weird. The waiter was inattentive sometimes and dismissive other times. The vibe was also strange, like they can't figure out who they are. Don't go there.