Samovar In Yerba Buena. It's a tea place, but has excellent food on the lighter side. I love their Egg Bowl and the Jook is good too. Scones made on the premises are excellent. Outdoor seating for sunny days with a nice view and a bit hard to find (above the waterfall) so usually not that crowded.
Right across the street from Moscone too. Just walk up the staircase from 4th and Howard and you're there.