Think of this fresh cake by Wendy Kromer as the food equivalent of the most intoxicating tropical drink you've ever had.
Split the two cake layers in half, horizontally. Set one layer on a corresponding-size cardboard round and pipe a dam of buttercream around its edge; fill with 2/3-3/4 cup passion fruit curd. Set another cake layer on top and finish filling accordingly. Set another cake layer on top, then crumb-coat using buttercream. Chill cake well, then spread on another layer or two of buttercream to give it a final coat.