Preheat oven to 350 degrees Fahrenheit and line the bottoms of three six-inch* round cake pans with parchment paper. Then, grease and flour the sides.
In a medium-sized bowl, whisk together the flour, baking powder, baking soda, salt, and spices.
In another medium bowl, whisk together both sugars, oil, pumpkin, eggs, and vanilla.
Add milk and whisk until combined.
Fold pineapple and carrots into the wet ingredients using a rubber spatula or wooden spoon.
Gradually add the flour mixture to the wet ingredients, folding together until incorporated.
Fold in the raisins, coconut, and walnuts.
Divide batter evenly between the three prepared cake pans. Bake at 350 F for 38-42 minutes**, or until a toothpick inserted into the center of the cakes comes out clean.
Remove cakes from oven and let cool in pans for about 15 minutes. Then, turn cakes out onto a wire cooling rack and let cool completely.***
Using a hand beater, or the paddle attachment of a stand mixer, beat butter and cream cheese together until light and fluffy.
Add powdered sugar gradually, about 1/2 cup at a time, beating on low speed until incorporated after each addition.
Add in vanilla, cinnamon, and salt, then beat until smooth.
Chill frosting for 15-20 minutes to help it firm up slightly.
Once cakes are completely cool, slice each layer in half horizontally using a sharp serrated knife. You will have six layers.
Spread a small amount of frosting on a cake board and place the first layer on top.
Top with a layer of frosting and spread evenly with an offset spatula. Top with second layer of cake and repeat with remaining four layers.
Chill cake for about 20 minutes, then frost top and sides of the cake with a thin layer of frosting, reserving enough for decorative piping if desired.
Use a large, open star piping tip to pipe rosettes on top of the cake and chill cake until ready to serve.
*You can also use 3 eight-inch round cake pans for this recipe, see baking time below.
**For 3 eight-inch layers, bake for 32-35 minutes.
***Once cakes are cooled, I recommend wrapping in saran wrap and chilling for a few hours for easier slicing and stacking.