Preheat oven and prep pan: Preheat the oven to 400°F and grease a 9-inch cast iron skillet or baking pan with butter or cooking spray. This keeps the edges from sticking and helps them turn crisp.
Mix the dry ingredients: In a large bowl, whisk together the cornmeal, flour, baking powder, baking soda, and salt until evenly combined. Set this bowl aside while you prepare the wet ingredients.
Mix the wet ingredients: In a separate bowl, stir together the mashed sweet potato, eggs, buttermilk, honey, and half of the melted butter until smooth. The mixture should look creamy and pale orange.
Combine the batter: Pour the wet mixture into the dry ingredients and fold together just until no dry streaks remain. A few small lumps are fine; overmixing makes the crumb dense.
Pour into the pan: Spread the batter evenly into the prepared skillet or pan, smoothing the top with a spatula so it bakes evenly.
Bake until golden: Bake for 22-25 minutes, until the top is golden brown, the edges pull slightly away from the pan, and a toothpick inserted in the center comes out clean.
Cool briefly in the pan: Let the cornbread rest in the pan for about 5 minutes. This short rest firms up the crumb enough to slice cleanly.
Make the honey butter: While the cornbread cools, beat the softened butter, honey, and salt together with a fork or hand mixer until light and fluffy.
Spread the honey butter on warm: Brush or spread half of the honey butter over the warm cornbread so it melts into the top and soaks slightly into the crumb.
Slice and serve: Cut the cornbread into squares and serve warm, with the remaining honey butter on the side for extra spreading.