Preheat your oven to 350°F (175°C).

Grease two 9-inch round cake pans with cooking spray and line the bottoms with parchment paper.

In a large bowl, whisk together the flour, sugar, baking powder, baking soda, cinnamon, and salt.

In another bowl, mix the oil and eggs until well combined.

Stir in the grated carrots and crushed pineapple into the wet mixture.

Gradually add the wet ingredients to the dry ingredients, mixing until just combined.

If using, fold in the chopped walnuts gently.

Divide the batter evenly between the prepared pans and bake for 30-35 minutes.

Check for doneness with a toothpick; it should come out clean.

Let the cakes cool in the pans for 10 minutes before transferring them to a wire rack.

In a bowl, mix the softened cream cheese and unsalted butter until smooth, then gradually add powdered sugar and vanilla extract to make frosting.

Once cakes are completely cool, frost the top of one cake layer, place the other layer on top, and frost the top and sides.