Preheat your oven to 400°F (200°C).
Cook sweet potatoes until tender, then mash until smooth, measuring out one cup.
In a large mixing bowl, combine all dry ingredients and whisk together.
In a separate bowl, whisk together wet ingredients until smooth.
Pour wet mixture into dry ingredients and gently fold until just combined.
Grease an 8-inch square baking pan and optionally mix melted butter with brown sugar, honey, salt, and cinnamon for the bottom.
Pour batter into the prepared pan and bake for about 40 minutes or until a toothpick comes out clean.