Looking for a children’s book (pre-1980) set in NYC with a Jewish friend named Ruthie

Hi! I’m trying to find a children’s or middle-grade book I read years ago—likely published before 1980. It was set in New York City, and the characters were two girls around 10 or 11 years old.

One of the girls was Jewish, and her name was Ruthie. The main character was not Jewish. I clearly remember a scene where the main character goes to Ruthie’s apartment and eats challah bread for the first time. It made a big impression on her.

Other details: • Written in third person • Set in an urban apartment building • Had a quiet, realistic tone (not fantasy or adventure) • Likely focused on friendship or coming-of-age

Does this ring a bell for anyone?