It’s a cake made mostly of air, sluiced in scents of sugar, white chocolate and lemon. Cooled, melted chocolate spun first into the batter, then into cream for the frosting. Doing her part to hold the fragile tower in line is homemade curd of Meyer lemons. Baked for a friend’s birthday 40-some years ago, I’ve tried twice to recreate the cunning confection. I woke this morning thinking that I should try to make this cake again. Then I remember how my neck and back turn to fire when I stand in...