For anyone who has had any contact with me for the last month, the idea of a lemon kefir tart shouldn’t come as a great surprise. I have, after all, spent that time all but obsessed with kefir, stashing mason jars of room-temperature milk all around the house, and watching gleefully as my grains — the live active culture — transform said milk into a thick, sweet, sour, sometimes slightly carbonated beverage.

What has set me down this path is a recent trip to New York, to visit Hana and her husband. Walking into their tiny Manhattan apartment, two things struck me almost at once: the happy, healthy, gigantic kombucha mother gurgling away in a jar on their counter, and the jar of kefir, just about done fermenting.