Chocolate pumpkin bundt cake

1 1/2 cups butter, softened

3 cups granulated sugar

6 large eggs

2 cups pumpkin purée

2 teaspoons vanilla

3 cups all purpose flour

1 Tbsp. Baking powder

1 teaspoon salt

1 teaspoon pumpkin pie spice

3/4 cup cocoa powder 

2/3 cup whole buttermilk 

Confectioners sugar

Preheat oven to 325 degrees. Spray a 15-cup bundt pan with baking spray with flour. In a large bowl, beat butter and sugar with a mixer at medium speed until fluffy. Add eggs, one at a time, beating well after each addition. 

Add pumpkin purée and vanilla. In another large bowl, whisk flour, baking powder, salt, and pie spice. Gradually add flour mixture to butter mixture, beating until combined. Spoon 2 cups batter into a medium bowl; whisk in cocoa and buttermilk until smooth. Spoon 1/3 of plain batter into prepared pan. Make a well In center of plain batter, add half of chocolate batter.  Repeat layers, ending with plain batter. Bake for 70-80 minutes. Let cool in pan for 5 minutes. Remove from pan and let cool. Sift with confectioners sugar just before serving.