To Make the Cake:

1. Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper.
2. In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, cinnamon, and salt.
3. Add the vegetable oil and eggs to the dry ingredients. Mix until well combined.
4. Fold in the grated carrots, crushed pineapple, and chopped nuts until evenly distributed.
5. Divide the batter evenly between the prepared cake pans.
6. Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.
7. Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.

To Make the Cream Cheese Frosting:

1. In a large bowl, beat the cream cheese and butter until smooth and creamy.
2. Gradually add the powdered sugar, one cup at a time, until the desired consistency is reached.
3. Stir in the vanilla extract and optional lemon juice for extra flavor.

To Assemble the Cake:

1. Place one cake layer on a serving plate and spread a generous amount of frosting on top.
2. Place the second layer on top and frost the entire cake.
3. Decorate with additional chopped nuts or grated carrots, if desired.