Invisible Apple Cake (Gâteau Invisible)

“Cake” is somewhat of a misnomer for this elegant dessert. Instead of open, airy and crumby, the texture is rich and dense, with slices of sweet-tart apples set in an egg-rich batter. During its long bake in the oven, the fruit slices and custard-like layers meld and become nearly indistinguishable from each other, giving the cake its name. We especially like Honeycrisp apples for this, as they have an ideal balance of sweetness and acidity, along with a texture that softens without turning mushy. Gala apples are the next best variety. To slice the fruits thinly and evenly, a mandoline is the tool of choice. If you prep them by hand, the slices should be no thicker than 1/16 inch. The cake is best the day it is baked, but make sure it has time to cool to room temperature before slicing and serving. Spiced caramel sauce and tangy whipped cream (recipes follow) are perfect accompaniments.