Preheat oven to 350°F.
Grease sides of two 9-inch round metal cake pans; line bottoms with parchment paper. Set aside.
In a large bowl, beat butter with sugar until light and fluffy; beat in eggs, 1 at a time, beating well after each. Beat in pumpkin and vanilla until incorporated.
In a separate bowl, whisk flour, ground pecans, baking soda, baking powder, salt, ginger, cinnamon, allspice and orange zest. Stir into butter mixture alternately with buttermilk, making 3 additions of dry ingredients and 2 of wet. Scrape into pans; smooth. Bake in the centre of oven until a cake tester comes out clean, about 25 to 30 minutes. Let cool in pans on rack for 10 minutes. Turn out onto racks; peel off paper. Invert; let cool.
For icing, in a large heavy skillet, melt butter over medium heat. Cook, stirring occasionally, until the butter turns a golden brown, about 4 minutes. Pour into a bowl and let stand until the little bits sink to the bottom, about 5 minutes. Transfer to freezer and chill until firm, about 15 minutes. Scrape the top of the butter from the bits at the bottom; discard bits.
Transfer brown butter to bowl with the cream cheese and brown sugar. With an electric mixer beat until the brown sugar has dissolved, about 2 minutes. Gradually beat in confectioner’s sugar until incorporated and fluffy, 1 to 2 minutes.
To assemble the cake, brush any crumbs from cake layers. Place 1 layer, on cake plate. Spread with about 1 cup of the icing. Sprinkle evenly with ½ cup of the candied pecans. Top with remaining cake, top-side down. Spread entire cake with a scant cup of the icing to mask. Refrigerate until firm, 30 minutes. Spread cake with remaining icing and decorate with remaining pecans.
Combine all ingredients except the pecans in a skillet and cook over medium heat for roughly two minutes, until the sugar is dissolved and the mixture is bubbling.
Add the pecans and cook for an additional 3 minutes, stirring to coat the pecans in the glaze.
Remove from the heat, and spread the pecans out on parchment paper to let the pecans cool completely. Break apart and use!
Recipe adapted from: Young, Nicole. "Pumpkin Pecan Cake with Brown Butter Icing." Food & Drink. Autumn 2011.