Preheat the oven to 350°F degrees. Line 3 6” cake pans or 2 8” cake pans with parchment rounds, spray with oil and lightly dust with flour. Set aside
Peel Carrots. Using a Food processor- grate carrots. Set aside.
In a medium bowl- combine all-purpose flour, baking soda, baking powder, spices, salt and whisk to combine.
In a stand mixer fitted with a paddle attachment- combine oil, granulated sugar, light brown sugar and mix until combined.
Add eggs one at a time, mixing until each egg is incorporated before adding the next egg. Add sweetened condensed milk and mix on medium speed for 30 seconds or until combined. *Skip this step if substituting with buttermilk.
Add dry ingredients to wet ingredients and mix on medium for 30 seconds- careful to not over mix the batter. Stop the mixer when a few ribbons of flour are visible and finish by folding the carrots and walnuts into the batter with a spatula. *If using buttermilk- add dry ingredients to the mixer, alternating with buttermilk. Beginning and ending with dry ingredients. Add 1/3 dry ingredients, mix. Add 1/2 buttermilk, mix. 1/3 dry ingredients, mix. Add the remainder of the buttermilk, mix. Add the remainder of the dry ingredients.
Evenly distribute the cake batter into each prepared cake pan and bake for 25- 35 minutes for 6” cake or 30-40 min for 8” cake. Check cakes by inserting a toothpick in the center. If it comes out clean or with a few crumbs- cakes are done!
Place on a cooling rack for 10 minutes in the pan before turning the cake pan upside down to release the cake to completely cool.
Prepare the buttercream