Preheat oven to 350°F
In a large mixing bowl, whisk together flour, cornmeal, baking powder, baking soda, salt, cinnamon, and nutmeg until well combined.
Use electric hand mixer or stand mixer fitted with whisk attachment to combine mashed sweet potato, brown sugar, granulated sugar, eggs, vegetable oil, melted butter, honey, vanilla extract, and milk. Start on low speed and gradually increase to medium speed. Mix until well combined, about 1 minute. Note: Discard any sweet potato strings caught in the whisk, don't put them back into the batter.
Pour wet ingredients into dry ingredients and whisk together until just moistened and no patches of dry ingredients remain. Try not to overmix.
Spray 9x9 baking dish with non-stick cooking spray. Pour in batter and spread evenly, then gently tap the bottom of the pan on the counter a few times to remove extra air before baking.
Bake at 350°F for 35-45 minutes, just until toothpick inserted in middle comes out clean.
Cool cornbread in pan until no longer hot. Cut and serve individual slices topped with butter and drizzled with honey, if desired.