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

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

In another bowl, beat together the granulated sugar, brown sugar, and vegetable oil until well combined. Add the eggs one at a time, mixing well after each addition. Stir in the grated carrots, crushed pistachios, and vanilla extract.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Divide the batter evenly between the prepared cake pans. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean. Let the cakes 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 medium bowl, beat together the softened cream cheese and butter until smooth. Gradually add the powdered sugar and vanilla extract, mixing until well combined. If the frosting is too thick, add milk one 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 cake layer on top. Frost the top and sides of the cake with the remaining cream cheese frosting. Garnish with additional crushed pistachios if desired.

Serve immediately or refrigerate for up to 3 days.