01 - Preheat oven to 350°F. Grease and line two 8-inch round cake pans with parchment paper.
02 - Whisk together flour, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt in a medium bowl.
03 - Whisk granulated sugar, brown sugar, oil, eggs, and vanilla extract in a large bowl until smooth.
04 - Gradually add dry ingredients to wet ingredients, mixing just until combined.
05 - Fold in grated carrots and chopped walnuts until evenly distributed.
06 - Divide batter evenly between prepared pans. Smooth the tops.
07 - Bake for 35-40 minutes, or until a toothpick inserted in the center comes out clean.
08 - Let cakes cool in pans for 10 minutes, then turn out onto a wire rack to cool completely.
09 - Beat cream cheese and butter together until creamy. Add powdered sugar, vanilla, and salt; beat until light and fluffy.
10 - Spread frosting layer on one cake, top with second layer, then frost top and sides. Decorate with extra walnuts if desired.