The oft-squabbling “Real Housewives of New York City” put their bickering aside Wednesday to celebrate cast member Ramona Singer‘s birthday at bistro Chat Noir on East 66th Street. But after the divas and 35-odd girlfriends got in the mood with Prosecco and Aperol cocktails, things took a darker turn. Instead of joking around, Singer talked up her favorite charities including “Sanctuary for Families,” which serves domestic violence victims and their children. Midway through her speech, she started to cry and revealed that her own father had physically abused her mother — and she was able to talk about it for the first time since his recent death. “In those days, you had nowhere to go,” the jewelry designer said of her painful childhood memories. Alex McCord, Bethenny Frankel, Jill Zarin, Kelly Bensimon, LuAnn de Lesseps and Sonja Morgan were visibly moved before moving on to “black cat” burgers, chicken and halibut.