Winter Citrus Upside-Down Cake

Citrus is at its prime in the winter months, so we love to use all the wonderful varieties in all the wonderful ways—including this upside-down cake, which has an almond flour-based batter and is topped with lightly sweetened labneh, a soft Middle Eastern cheese that we have used in a few savory recipes in this book. The flavor is reminiscent of a Creamsicle, while the presentation is a sophisticated showstopper. We incorporate two varieties of orange, a grapefruit, and kumquats in this sea