Tropical Wedding Cake - Martha Stewart. The yellow-cake layers are brushed with rum syrup and filled with passion-fruit curd and rum-and-vanilla-bean buttercream. The top of each tier is spread with more passion-fruit curd. Hibiscus flowers, lychees, coconut, crown the cake. Pressing a straw mat into the fondant produces textured appearance. Serve with a slice of fruit such as star fruit, and coconut sorbet.