Prepare cake pans: Preheat oven to 350 degrees F. Lightly coat three 8-inch cake pans with softened butter. Cut three 8-inch circles out of parchment paper and fit them into the bottom of the cake pans. Lightly coat the paper circles with butter and set aside.
Make the batter: Cream butter until smooth in a large bowl with an electric mixer set on medium speed. Add the sugars and mix until smooth. Add eggs, one at a time, beating well after each addition, until the mixture is smooth and light. Set aside. Combine the pumpkin purée, buttermilk, and vanilla in a medium bowl and set aside. Combine the flour, baking powder, cinnamon, baking soda, and nutmeg in a large bowl and set aside. In thirds, alternately add the flour mixture and buttermilk mixture to the butter mixture, blending well after each addition until smooth.
Bake the cake: Pour batter into the prepared pans and bake until a toothpick inserted into the middle of each cake comes out clean - 35 to 40 minutes. Cool the cakes in the pan on wire racks for 30 minutes. Remove cakes from pans and return to the wire racks until completely cool. Assemble the cake: Place one layer on a cake plate and top with one-third recipe of Pumpkin Cream-Cheese Frosting. Repeat with the second and third layers. Serve or store refrigerated for up to four days.
Directions for Frosting:.
Blend the cream cheese, pumpkin purée, butter, orange juice, zest, and vanilla in a large bowl using an electric mixer set at medium speed until smooth. Add the sugar and continue to beat until light and creamy - about 5 more minutes.