Preheat the oven to 350°F. Grease three 6-inch round cake pans and line the bottoms with parchment paper.
In a medium bowl, whisk together flour, cinnamon, nutmeg, ginger, allspice, baking powder, baking soda, and salt.
In a large bowl, cream together butter, granulated sugar, and brown sugar until fluffy.
Add eggs and vanilla, mixing until smooth and slightly fluffy.
Alternate adding dry ingredients and buttermilk to the butter mixture, mixing until smooth.
Fold in shredded carrots.
Divide batter among prepared cake pans and bake for 36-41 minutes.
Let cakes cool in pans for 5 minutes, then transfer to wire racks to cool completely.