Step 1: Preheat your oven to 350°F (175°C) and generously grease two 6-cavity doughnut pans with non-stick spray or butter.
Step 2: In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, ginger, and nutmeg until well combined.
Step 3: In a separate medium bowl, whisk the sweet potato puree with the brown sugar, granulated sugar, eggs, milk, melted butter, and vanilla extract until smooth.
Step 4: Gently fold the wet ingredients into the dry ingredients using a spatula, mixing only until no streaks of flour remain to keep the spiced sweet potato doughnuts recipe texture light.
Step 5: Transfer the batter to a piping bag and fill each doughnut cavity about 3/4 full.
Step 6: Bake for 12-15 minutes, or until a toothpick inserted into the center comes out clean.
Step 7: Allow the doughnuts to cool in the pan for 5 minutes before transferring them to a wire rack. While still warm, coat with additional cinnamon sugar if desired.