Step 1: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or a 9x13 inch baking pan. Line the bottom with parchment paper if using round pans.
Step 2: In a large bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg. Set aside.
Step 3: In a separate large bowl, beat the eggs until light. Gradually add the granulated sugar and brown sugar, beating until the mixture is light and fluffy.
Step 4: Slowly stream in the vegetable oil and vanilla extract, mixing until just combined. Do not overmix.
Step 5: Gradually add the dry ingredients to the wet ingredients, mixing on low speed or by hand until just combined. Be careful not to overmix the batter.
Step 6: Fold in the freshly grated carrots, and any optional add-ins like nuts, raisins, or drained pineapple, until evenly distributed.
Step 7: Pour the batter evenly into the prepared cake pans. Bake for 30-35 minutes for round pans, or 40-45 minutes for a 9x13 inch pan, or until a wooden skewer inserted into the center comes out clean.
Step 8: Let the cakes cool in the pans for 10-15 minutes before inverting them onto a wire rack to cool completely. Ensure they are fully cooled before frosting.
Step 9: While the cakes cool, prepare the cream cheese frosting. In a large bowl, beat the softened butter and cream cheese together until smooth and creamy. Ensure there are no lumps.
Step 10: Gradually add the sifted powdered sugar, 1 cup at a time, beating until smooth after each addition. Mix in the vanilla extract and a pinch of salt. Beat until the frosting is light and fluffy.
Step 11: Once the cakes are completely cool, spread the cream cheese frosting evenly over the top and sides of the cake. Garnish with additional chopped nuts or carrot curls if desired. Slice and serve!