Preheat oven to 350ºF (180°C).
Grease (use shortening) and flour a large 10 or 12-cup bundt pan.
In a bowl sift together flour, baking powder, soda, spices, and salt.
Cream softened butter in a large bowl adding both sugars gradually, and beat for 2-3 minutes, until thick and fluffy.
Add the eggs, one at a time, beating after each addition until well incorporated.
Add vanilla, the sweet potato puree, and mix well.
Add the sifted flour mixture in two additions alternating with the buttermilk, beating only until well mixed. It's important that you don't overbeat the sweet potato mixture at this point.
Pour batter into the prepared pan and smooth the top.
Bake for 50-60 minutes, or until a cake tester or toothpick inserted in the middle of the cake comes out clean. If the top is browning too quickly before it's done, loosely cover the cake with a large piece of aluminum foil so the top doesn't continue to brown while the inside bakes fully.
Let cool for about 15 minutes in the pan on a wire rack. Grab the pan with kitchen towels and starts shaking it a little, until the cake moves and you make sure the bottom and sides are not stuck.
Invert onto a wire rack, and cool completely before frosting.
Pour the maple glaze and let it drip down the sides. If sprinkling chopped pecans or ground cinnamon to decorate, do so before the glaze sets.