Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans.

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

In a separate bowl, beat together the sugar, eggs, and vegetable oil until smooth.

Stir in the shredded carrots and drained pineapple into the wet mixture.

Gradually add the dry mixture to the wet mixture, folding until just combined.

If desired, fold in the chopped walnuts.

Divide the batter between the prepared cake pans and bake for 30-35 minutes until a toothpick comes out clean.

Allow the cakes to cool in the pans for about 10 minutes before turning them out onto wire racks to cool completely.

While cooling, prepare the cream cheese frosting by mixing the cream cheese and butter until smooth, then gradually add powdered sugar and vanilla, adjusting with milk if needed.

Once cooled, frost the top of one cake layer, place the second layer on top, and frost the sides and top of the entire cake.