How to Make It
Preheat the oven to 350°. Grease two 8-inch round cake pans and line the bottoms with parchment paper.
Place 4 cups of the coconut in a blender; pulse until finely ground. Spread the ground coconut on a baking sheet. On a separate baking sheet, spread the remaining coconut. Toast both sheets for 7 to 8 minutes, stirring occasionally, until lightly golden; let cool.
Into a large bowl, sift the cake flour, baking powder and baking soda. In another large bowl, using an electric mixer, cream the 1 1/2 sticks of butter with the coconut oil, sugar, salt and cardamom at medium-high speed until light, 3 minutes. Beat in the ground toasted coconut. Beat in the eggs, one at a time, until incorporated. At low speed, beat in the flour mixture and buttermilk in 3 alternating batches, starting and ending with the flour.
Divide the batter evenly between the 2 pans. Bake for 50 to 60 minutes, until the cakes are deep golden and springy. Transfer the cakes to a rack and cool. Turn the cakes out and peel off the parchment. Cut each cake in half horizontally to create 4 layers.
In a large saucepan, boil the sugar, honey and 3/4 cup of water over moderately high heat until the syrup registers 240°. Meanwhile, in the bowl of a stand mixer fitted with the whisk, beat the egg whites at medium speed until foamy; beat in the salt and cream of tartar until soft peaks form. With the mixer on, drizzle the hot syrup down the side of the bowl. Once all of the syrup has been added, beat the frosting at high speed until shiny and thick, 11 minutes. Cool.
Set a cake layer cut side up on a plate. Spread one-third of the marmalade over the top, then spread with 1/2 cup of the frosting; repeat with 2 more cake layers. Top with the last layer. Coat the cake with the remaining frosting. Cover with the toasted coconut.