A lush combination of a Southern upside-down cake and a French tarte tatin, this cake is deeply caramelized on top and light and fluffy beneath. The chef Virginia Willis, who put the recipe together, uses a whole vanilla bean, but if you don't feel like making that investment, a teaspoon of strong pure vanilla extract is fine. She uses a well-seasoned cast-iron skillet, but a heavy nonstick one would work too. The whipped cream is optional, as is the bourbon that brightens it; you can add vanilla, confectioners' sugar or both if you prefer.