A Moon for Moe and Mo by Jane Breskin Zalben
From Charlesbridge Publishing:
An interfaith friendship develops when Rosh Hashanah, the Jewish New Year, overlaps with the Muslim holiday of Ramadan—an occurence that happens only once every thirty years or so.
Moses Feldman, a Jewish boy, lives at one end of Flatbush Avenue in Brooklyn, New York, while Mohammed Hassan, a Muslim boy, lives at the other. One day they meet at Sahadi's market while out shopping with their mothers and are mistaken for brothers. A friendship is born, and the boys bring their families together to share rugelach and date cookies in the park as they make a wish for peace.