Preheat oven to 400°F. Spray a 6-cup mini-bundt pan with cooking spray or lightly coat with oil. Sprinkle molds with 3 tablespoons sugar, tapping out excess.
In a large bowl, combine flours, xanthan gum, cinnamon, nutmeg, baking powder, baking soda, and salt. Set aside.
In another bowl, whisk together the egg (or tofu – see below), buttermilk, brown sugar, pumpkin, oil, and lemon peel until very, very smooth. Add dry ingredients and stir just until combined.
Spoon 1/4-cup batter into prepared molds. Bake 15-18 minutes or until doughnuts brown around edges. Cool 2 minutes. Then loosen edges and invert doughnuts onto wire rack to cool. Repeat with remaining half of batter.
