Step 1: Prepare Cream Cheese Frosting

To make cream cheese frosting, in a large bowl add cream cheese, unsalted butter and beat just until well blended with no lumps. Gradually add confectioner's sugar and beat until fully incorporated and smooth. Add vanilla extract, lemon zest and beat everything together till smooth. Divide 1/4 cups of cream cheese frosting into two small bowls then add orange food coloring, green food coloring in it and mix it well. Keep rest of the cream cheese frosting to frost the whole carrot cake.

Step 2: Prepare Carrot Cake Batter

To make carrot cake batter, in a large bowl add all-purpose flour, baking soda, baking powder, salt, ground cinnamon and stir it well. In a another large bowl add eggs and beat until frothy. Add granulated white sugar, vegetable oil, vanilla extract and beat until mixture is thick and light colored. Then add flour mixture and beat just until incorporated. Stir in the grated carrots and one cup of toasted chopped walnut.

Step 3: Bake Carrot Cake

To bake carrot cake, preheat oven to 350F. Grease and butter two cake pans. Evenly divide carrot cake batter between the two prepared cake pans. Place cake pans in the oven and bake for 30 minutes. Remove cake pans from the oven and allow it to cool for 10 minutes.

Step 4: Assemble and Decorate Carrot Cake

To assemble and decorate carrot cake, place carrot cake bun on a serving plate. Then spread with about ? of the cream cheese frosting. Gently place another carrot cake bun on the cream cheese frosting and spread rest of the cream cheese frosting over the top and sides of the carrot cake. Decorate carrot cake with orange and green colored cream cheese frosting. Press toasted chopped walnuts on the side wall of the carrot cake. Your yummy Carrot Cake is ready to eat!