Melt the butter either in a large mixing bowl and let cool slightly.
Combine the flour, sugar, baking soda, salt, and spices in a separate bowl. Add to the butter and mix well.
Whisk the eggs, vanilla, and buttermilk in a large measuring cup or bowl and add to the batter. Fold in the carrots and walnuts.
Transfer to your loaf pan and bake for 45-50 minutes, until top is browned and a toothpick inserted in the center comes out clean.
Let the cake cool completely before frosting.
To make the frosting, whisk the cream cheese and butter together and slowly add the powdered sugar. Whisk until smooth and add the cream and maple extract.
Frost the cake with a thick layer of frosting before slicing and serving.