Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, salt, cinnamon, and nutmeg.
In another bowl, combine the vegetable oil and eggs, whisking until well blended. Stir in the grated carrots, crushed pineapple, and optional walnuts and coconut.
Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Do not overmix.
Divide the batter evenly between the prepared cake pans. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans for 10 minutes, then transfer to wire racks to cool completely.
While the cakes are cooling, prepare the cream cheese frosting. In a mixing bowl, beat the softened cream cheese and butter together until smooth. Gradually add the powdered sugar and vanilla extract, mixing until creamy. If the frosting is too thick, add milk a tablespoon at a time until desired consistency is reached.
Once the cakes are completely cool, place one layer on a serving plate. Spread a layer of cream cheese frosting on top, then place the second layer on top and frost the top and sides of the cake.