2teaspoonsorange liqueur, or 1/2 teaspoon orange extract
Preheat the oven to 350°F and generously grease two 8-inch round cake pans.
Measure the sifted flour into a bowl. Add the baking powder, salt, baking soda, cinnamon, ginger and allspice. Sift together a second time.
Place the butter, brown sugar and granulated sugar in mixing bowl. Using an electric mixer on low, cream together until smoooth. Add the eggs and beat on medium speed until light and fluffy.
Mix in the dry ingredients alternately with the buttermilk, beating until smooth after each addition. Add the pumpkin and combine thoroughly.
Pour the batter into the prepared cake pans and bake for 20 to 25 minutes, or until a toothpick inserted in the center of the cake comes out clean.
Cool 10 minutes in the pans, then turn onto racks and cool completely.
While the cake cools, prepare the frosting. Place the cream cheese, butter, 3 cups of the confectioners' sugar, orange zest, cinnamon and orange liqueur in a large mixing bowl. Beat with an electric mixer on medium until smooth and creamy, adding a little additional confectioners' sugar if necessary.
Once the cake is cooled completely, frost the tops of both layers and sprinkle the top layer with the toasted walnuts.