1. Preheat and Prepare: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line the bottoms with parchment paper.
2. Mix Dry Ingredients: In a large bowl, whisk together the flour, sugar, baking powder, baking soda, cinnamon, and salt.
3. Combine Wet Ingredients: In a separate bowl, whisk together the eggs, vegetable oil, and vanilla extract until smooth and well-blended.
4. Add Carrots and Pineapple: Stir in the grated carrots and crushed pineapple into the wet mixture until evenly combined.
5. Combine Wet and Dry Mixtures: Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Avoid overmixing to ensure the cake stays light and fluffy.
6. Add Nuts: If using, fold in the chopped walnuts or pecans.
7. Bake: Divide the batter evenly between the prepared pans, smoothing the tops with a spatula. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
8. Cool: Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely before frosting.

For the Cream Cheese Frosting

1. Beat Cream Cheese and Butter: In a large mixing bowl, beat the softened cream cheese and butter until creamy and smooth.
2. Add Powdered Sugar: Gradually add the powdered sugar, one cup at a time, until fully incorporated and the frosting reaches your desired sweetness.
3. Add Vanilla and Lemon Juice: Stir in the vanilla extract and, if desired, a splash of lemon juice for extra brightness.
4. Whip: Beat the frosting on high speed for a few minutes to make it light and fluffy.

Assembling the Cake

1. Frost the First Layer: Place one cake layer on a serving plate. Spread a generous amount of cream cheese frosting over the top.
2. Add the Second Layer: Place the second cake layer on top of the frosted layer.
3. Frost the Entire Cake: Spread the remaining frosting over the top and sides of the cake.
4. Decorate: Optionally, garnish with additional chopped nuts, shredded coconut, or thin strips of carrot for decoration.