In an electric mixer fitted with a paddle attachment, mix pumpkin, eggs, brown sugar, cooled melted butter, Butterscotch syrup and vanilla until smooth.
Stir together the flour, baking powder, baking soda, salt, and spices.
Gradually add flour mixture to mixer and beat until you have a smooth batter.
Fold in the chopped walnuts.
Line three 8-inch cake pans with parchment and spray bottom and sides with baker's release spray.
Add 3-1/2 cups of batter to each pan.
Bake in the preheated oven for 15 minutes, then rotate the pans and bake for 10-15 minutes more, or until cakes test done.
Let the cakes cool for ten minutes in the pans, then turn them out and finish cooling on a wire rack. Discard parchment underneath.
Level cakes with a serrated knife.
Stack bottom layer, top with 1/4 cup apple butter, then 1/4 cup Butterscotch frosting.
Top with another layer and repeat.
Place the last cake on upside down and frost an initial layer on top and sides, scraping off excess.
Chill one hour, then finish applying frosting.
Decorate with autumn sprinkles and candy pumpkins.