Preheat Oven: Set your oven to 350°F (180°C). Grease your cake pans (either a 9x13 pan or two 9-inch round pans).
Mix Wet Ingredients: In a large bowl, whisk together the white sugar, light brown sugar, eggs, and oil until well combined.
Prepare Dry Ingredients: In another bowl, combine the flour, baking powder, baking soda, cinnamon, nutmeg, and grated carrots.
Combine: Gradually mix the dry ingredients into the wet mixture until well combined. Optionally, fold in raisins.
Bake: Pour the batter into the prepared pans. Bake for about 40 minutes, or until a toothpick inserted into the center comes out clean.
Cool: Let the cakes cool in the pans for about 10 minutes, then transfer them to a wire rack to cool completely.
Make Frosting: Beat the cream cheese and butter until smooth. Gradually add the powdered sugar and vanilla extract, mixing until smooth.
Frost: Once the cakes are completely cool, spread the cream cheese frosting over the top and sides.