Preheat oven to 375 degrees. Lightly spray two miniature doughnut pans with cooking spray, set aside.
In a large bowl combine the sugar, egg, butter, buttermilk, sour cream, lemon zest, vanilla. Gently mix until combined.
In a separate mixing bowl, whisk together the cake flour, baking powder, baking soda, cinnamon, nutmeg and salt. Slowly incorporated the dry ingredients into the wet ingredients, being careful not to create large clumps (I poured and stirred about 6 times). Stir until combined, do not overmix!
Once the batter has come together, place into a large ziplock bag or a pastry bag fitted with a large circular tip. If using the ziplock back, cut one corner and pipe into the prepared pans.
Bake for 8-10 minutes, remove from the oven. Cool in the pans for 3-4 minutes, then pour the powdered sugar into a large ziplock bag and toss in one pan of donettes at a time. Shake until thoroughly coated. Remove, set aside and repeat with the remaining pan of donettes. Enjoy immediately.