A classic carrot cake with a hint of cinnamon, nutmeg and ginger.
Place oven rack in center position. Preheat oven to 350 degrees. Use a paper towel to wipe bottom and sides of non stick pan with butter. Coat with flour and set aside.
In a bowl, whisk together flour, baking powder, baking soda, sea salt, cinnamon, ginger, and nutmeg, set aside.
Place sugars and butter in mixing bowl and mix until well combined.
Add eggs one at a time, mix well.
Add grated carrots, mix until well combined. Add flour mixture, cranberries and 1/2 cup walnuts (reserving the rest for the top of cake) Mix very well
Pour equal amounts of batter into pans, tap on counter to remove any bubbles. If using 3-8" pans bake for 25-30 minutes or until an inserted toothpick comes out clean. If using 2-9" pans bake for 30-35 minutes, or until an inserted toothpick comes out clean.
Remove pans from oven and allow to completely cool. Very carefully remove one cake from pan, (these cakes are fairly fragile) Place first layer upside down in center of a cake plate, spread with cream cheese frosting, add second layer (again, upside down) frost, add third layer, frost, then frost sides. Sprinkle top of cake with reserved walnuts.
Mix together butter and cream cheese until smooth. Add powdered sugar and 1 tablespoon buttermilk. Mix until smooth. If needed, add second tablespoon of buttermilk.