Preheat your oven to 350°F (175°C). In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, cinnamon, and salt until well combined.

In another bowl, mix oil, eggs, grated carrots, and crushed pineapple. Slowly combine wet and dry ingredients until just blended.

Fold in chopped walnuts and vanilla extract into the batter gently to retain the fluffy texture.

Grease and flour two 9-inch round cake pans. Pour the batter evenly into the prepared pans and smooth the tops. Bake for 25-30 minutes.

Remove the cake layers from the oven and allow them to cool in the pans for about 10 minutes. Then, invert the cakes onto wire racks to cool completely.

In a mixing bowl, beat together softened cream cheese and unsalted butter until smooth. Gradually add powdered sugar until fluffy. Stir in vanilla extract.

Once the cake layers are cooled, place one layer on a serving platter. Spread frosting on top, place the second layer on top, and cover the cake with remaining frosting.

Sprinkle optional toppings like shredded coconut or chopped walnuts for an appealing finish before slicing and serving.