This twist on fruitcake will appeal to fruitcake lovers and haters alike.
Heat oven to 350 degrees with racks placed in center. Spread nuts on a baking pan. Bake until fragrant, about 7 minutes. Transfer nuts to a bowl; set aside to cool.
Line the bottoms of three 8-by-2-inch buttered cake pans with parchment paper, and butter the parchment. Dust the bottoms and sides of pan with flour, and tap out any excess. In a large bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside. Finely chop the raisins, and combine with the cinnamon and allspice. Set aside.
With an electric mixer fitted with the paddle attachment, beat together the sugar and shortening on medium speed until combined. Add eggs one at a time, beating well after each addition. On low speed, add the flour mixture and the milk to the batter, alternating between the two, starting and ending with the dry ingredients.
Fold the reserved raisin mixture into one-third of the batter. Pour batter into one cake pan. Stir the reserved toasted walnuts into the remaining batter. Divide batter between two remaining cake pans. Bake, rotating pans for even baking if necessary, until a cake tester inserted in the middle comes out clean, about 40 minutes. Transfer to cooling racks to cool, and invert cakes onto cooling rack. Allow to cool completely.
Combine the pineapple, oranges, 2 cups coconut, and sugar in a medium saucepan. Bring filling to a boil over high heat, stirring. Reduce to a simmer, and let cook, stirring often, until thickened, about 20 minutes. Whisk the cornstarch into 1/4 cup warm water. Stir into filling. Continue to cook until thick, 6 minutes. Let cool before using.
Place one walnut layer top-side down on the serving plate. Top with half of the filling. Place the raisin layer, top-side up, securely on top, press down lightly. Using an offset spatula, go around the layers to press filling between layers. Top with remaining filling. Place remaining walnut layer on top, top-side up. Press down with hands. Using the offset spatula, go around layers again to ensure filling is securely between layers. Frost the sides of the cake first, using an offset spatula. Finish icing the top of the cake. Decorate top of cake with drained candied orange zest and remaining coconut. Serve.
This cake is not a traditional fruitcake but a delicious three-layer spice cake. Use three 8-by-2-inch-deep cake pans to make each of the layers. The filling may be made a day ahead.