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

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

In another bowl, blend sugar, eggs, and oil until smooth, about 2-3 minutes.

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

Gradually fold in dry ingredients until just combined, avoid overmixing.

If using, fold chopped walnuts into the batter.

Divide batter evenly between prepared pans and smooth the tops.

Bake for 30-35 minutes, checking for doneness with a toothpick.

Let cakes cool in pans for 10 minutes, then transfer to wire racks to cool completely.

Beat cream cheese and butter until creamy, then incorporate powdered sugar and vanilla.

Once cooled, frost the top of one cake layer and stack the second layer on top, frosting the sides and top.

Slice and serve, optionally garnishing with walnuts or fresh fruit.