Step 1: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line with parchment paper circles on the bottoms. This ensures the Hawaiian Carrot Pineapple Cake Cream Cheese Frosting layers release easily.
Step 2: In a large bowl, whisk together the flour, granulated sugar, baking soda, ground cinnamon, ground nutmeg, and salt until well combined. This distributes the dry ingredients evenly.
Step 3: In a separate medium bowl, whisk together the vegetable oil, eggs (adding one at a time and mixing well after each), and vanilla extract.
Step 4: Pour the wet ingredients into the dry ingredients. Mix on low speed with an electric mixer or by hand with a whisk until just combined. Do not overmix; a few lumps are fine for this Hawaiian Carrot Pineapple Cake Cream Cheese Frosting batter.
Step 5: Fold in the well-drained crushed pineapple and grated carrots. If using, also fold in chopped nuts and/or shredded coconut until evenly distributed.
Step 6: Divide the batter evenly between the two prepared cake pans.
Step 7: Bake for 30-35 minutes, or until a wooden skewer or toothpick inserted into the center of the cakes comes out clean. Baking time may vary slightly depending on your oven.
Step 8: Let the cake layers cool in the pans for 10-15 minutes before inverting them onto a wire rack to cool completely. It's crucial that the Hawaiian Carrot Pineapple Cake Cream Cheese Frosting layers are fully cooled before frosting.
Step 9: While the cakes cool, prepare the cream cheese frosting: In a large bowl, beat the softened cream cheese and softened unsalted butter with an electric mixer on medium speed until smooth and creamy, about 2-3 minutes. Ensure there are no lumps.
Step 10: Gradually add the sifted powdered sugar to the cream cheese mixture, beating on low speed until combined, then increase to medium-high and beat until the frosting is light and fluffy, another 2-3 minutes.
Step 11: Beat in the vanilla extract. If the frosting is too thick, add milk or heavy cream one teaspoon at a time until it reaches your desired spreading consistency for your Hawaiian Carrot Pineapple Cake Cream Cheese Frosting.
Step 12: Once the cake layers are completely cool, place one layer on your serving platter. Spread a generous amount of cream cheese frosting over the top.
Step 13: Carefully place the second cake layer on top. Frost the top and sides of the entire Hawaiian Carrot Pineapple Cake Cream Cheese Frosting, using an offset spatula or knife to create smooth sides or decorative swirls.
Step 14: Garnish with additional chopped pecans, shredded coconut, or pineapple tidbits, if desired. For best results, chill the Hawaiian Carrot Pineapple Cake Cream Cheese Frosting in the refrigerator for at least 30 minutes before serving. Store leftovers in an airtight container in the refrigerator.