Preheat oven to 350 degrees F. Spray two 9 inch circle pans with non-stick spray, and add parchment paper to the bottom and a light dusting of flour to the sides if desired (this helps to remove the cakes).
Add flour, cinnamon, nutmeg, baking powder, baking soda and salt to a bowl and mix well. Add a couple tablespoons of dry mixture to pecans if using and mix well**.
In a separate bowl, add the oil, brown sugar, cane sugar, plant milk, flax eggs and vanilla and mix well.
Add dry ingredients to wet ingredients and mix just until incorporated, it's okay if there are a few dry bits left because you don't want to over mix.
Add the grated carrots and pecans and mix until evenly distributed.
Pour evenly into two 9 inch circle pans, and then bake for 33-38 minutes, or until a toothpick inserted into the center of the cake comes out clean!
Let the cakes cool in the pan for 10-15 minutes, and then transfer to a cooling rack to cool completely.
While you wait, start on the frosting: add the room temperature vegan butter and vanilla to a bowl and mix with an electric mixer or vigorously by hand until creamy. Add the powdered sugar in 2-3 increments, mixing in between.
If frosting is a bit too thick, add the smallest amount of plant milk needed to make it easier to frost.
Once cakes are completely cooled, add half the frosting to the top of one cake and spread around evenly. Carefully add the second cake on top and the remaining frosting, spreading evenly again.
Top with more pecans if desired and enjoy!