Step 1: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round baking pans. Set aside.
Step 2: In a large bowl, whisk together the dry ingredients: all-purpose flour, baking soda, baking powder, cinnamon, nutmeg, and salt. Set aside.
Step 3: In a separate large bowl, mix together the wet ingredients: eggs, vegetable oil, granulated sugar, and brown sugar. Whisk until well combined and smooth.
Step 4: Gradually add the dry ingredient mixture to the wet mixture. Mix just until combined, being careful not to overmix. A few lumps are fine.
Step 5: Gently fold in the finely grated carrots and any optional add-ins like crushed pineapple, chopped nuts, or shredded coconut, ensuring they are evenly distributed.
Step 6: Divide the batter evenly between the two prepared 9-inch round pans.
Step 7: Bake for 30-35 minutes, or until a wooden skewer or toothpick inserted into the center of the cakes comes out clean.
Step 8: Remove the cakes from the oven and let them cool in their pans on a wire rack for 10-15 minutes. After this initial cooling, carefully invert the cakes onto the wire rack to cool completely.
Step 9: For the cream cheese frosting: In a large bowl, beat the softened cream cheese and butter together with an electric mixer until light and fluffy (about 2-3 minutes).
Step 10: Gradually add the sifted powdered sugar, one cup at a time, beating well after each addition. Once all sugar is incorporated, add the vanilla extract and beat on medium-high speed for another 1-2 minutes until smooth and creamy.
Step 11: Once cake layers are completely cool, apply a thin crumb coat of frosting to seal any crumbs. Chill for 15-20 minutes, then apply the remaining frosting evenly over the top and sides of the cake. Garnish with extra chopped nuts or coconut if desired.