Prepare the Sweet Potato Puree:
Peel and cut fresh sweet potatoes into cubes.
Boil for about 10 minutes until tender.
Let cool for 25 minutes.
Blend in a food processor until smooth.
Mixing Dry Ingredients:
In a large bowl, combine yellow cornmeal, flour, baking powder, baking soda, salt, cinnamon, nutmeg, and clove.
Mixing Wet Ingredients:
In another bowl, whisk together sweet potato puree, buttermilk, eggs, egg yolk, vegetable oil, melted butter, and vanilla extract.
Combine Wet and Dry Ingredients:
Gradually add wet ingredients to dry ingredients.
Stir until just combined (do not overmix).
Baking the Cornbread:
Preheat oven to 400°F.
Pour batter into a greased baking dish or cast-iron skillet.
Smooth the top with a spatula.
Bake for 25-30 minutes.
Check with a toothpick; if it comes out clean, it's ready.