This moist cake combines the typical carrot cake flavor with ginger and a creamy orange filling.
Preheat the oven to 350 degrees Fahrenheit and grease and flour two 9" round cake pans.
Peel and cut carrots into 1-1/2 inch pieces and cover with water in a small sauce pan. Boil until they are tender when you poke them with a fork. Drain the carrots and place them in a blender with the buttermilk. Blend until smooth.
Pour into a bowl and add the sugar, eggs, fresh ginger, vanilla, orange zest, and oil. Beat until smooth.
Sift in the flour, baking soda, cinnamon, ginger and salt. Stir until combined.
Divide the batter between the two pans. Bake for about 30 minutes, until a toothpick comes out clean. Allow to cool for about 20 minutes and then turn out onto a cake plate to finish cooling.
Combine all ingredients and beat with an electric or hand mixer until smooth.
Level one of the cakes by taking a bread knife and sliding it horizontally, cutting off the rounded top. Spread the filling on the flat surface of the cake. Carefully place the other cake on top of it.
Mix the butter, sugar, and vanilla and 1/4 cup of the sour cream in a bowl with a hand or electric mixer. Add more sour cream as needed until the icing is light and fluffy.
Ice the top and sides of the cake with the buttercream. You could also use cream cheese frosting. Refrigerate for 1 hour to help the icing set.