Good place in St. Peterburg
Try the Zhababar on the corner of Kazanskaya and Gorokhovaya. Had a superlative meal, including entree, drink (prosecco), and dessert for $32 pp. This is cheap for a fine meal in Russia. Entrees included salmon-filled blini, medallions of veal with a wine sauce, excellent salads in an otherwise salad-starved country, and the best cheesecake (chis kek) of your life. Highly recommended!
For a nice, filling, cheaper lunch (blinchiki), try the Samovar across the street on Gorokhovaya. It doesn't have as many filling choices as other blinnayas in town, but those they had were delicious (mushroom and potato, ham and mushroom---don't miss the sweet cheese (tvorog) filling, drizzled with honey).