in a medium mixing bowl, whisk together the cornmeal, flour, baking soda, baking powder, salt, Set aside.
In a large bowl, combine together the sugars, vegetable oil, and melted butter until smooth. Then whisk in one egg at a time - add the sweet potato purée, Whisk in your sour cream and buttermilk, stirring until fully combined.
Gently fold the dry ingredients into the wet ingredients, mixing just until incorporated. Avoid overmixing to keep the cornbread tender.
Pour the batter into the prepared pan or skillet, smoothing the top. Bake for 25-30 minutes (mine took 30 minutes), or until a toothpick inserted in the center comes out clean and the top is golden.