Follow these simple steps to create your Carrot Sheet Cake:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan.
2. Mix Dry Ingredients: In a large bowl, whisk together the flour, sugar, baking soda, baking powder, cinnamon, nutmeg, and salt.
3. Combine Wet Ingredients: In another bowl, combine the vegetable oil and eggs, whisking until well blended.
4. Add Carrots: Stir in the grated carrots and crushed pineapple, if using, into the wet mixture.
5. Combine Mixtures: Gradually add the wet ingredients to the dry ingredients. Mix until just combined.
6. Add Nuts: Fold in the chopped walnuts or pecans if desired for added texture.
7. Pour Batter: Pour the batter into the prepared baking pan, spreading it evenly.
8. Bake: Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
9. Cool: Remove from the oven and allow the cake to cool in the pan for 15-20 minutes before transferring to a wire rack to cool completely.
10. Prepare Frosting: In a mixing bowl, beat together the softened cream cheese and butter until smooth. Gradually add powdered sugar and vanilla extract, beating until creamy. Add milk as needed to achieve desired consistency.
11. Frost Cake: Once the cake is completely cool, spread the cream cheese frosting evenly over the top.