Step 1

In a large bowl, combine the flour, baking powder, baking soda, and salt, and mix well. In the mixing bowl of a stand mixer, with the whisk attachment, mix the eggs, lemon zest, sugar, oil, buttermilk, sour cream, and vanilla, until all ingredients are well blended.

Step 2

Add the flour mixture a little at a time to the mixing bowl, mixing on low between additions, and until all flour has been mixed. Scrape down sides of mixing bowl, and stir in any ingredients that were not blended. Gently, with a rubber spatula, fold the blueberries into the batter, just until mixed - Do not over-mix.

Step 3

Let the batter rest for 5 minutes. In a small bowl, mix the cinnamon and sugar for dipping, and set aside. Spray 2 doughnut pans 6 - 12 count, with cooking spray, and set aside.

Step 4

Turn on oven to 400 degrees. If your mixing bowl has a pouring spout, then use the bowl to fill the doughnut pans, if not; place a large heavy-duty Ziploc bag into a bowl, or large glass, and pour the batter into the Ziploc bag.

Step 5

Make sure the bag is zipped completely, and carefully move the batter away from the bottom of the bag, and snip one corner off the bag. Fill the doughnut pans half to 3/4 full with the batter, and bake for 10 to 15 minutes, or until the dough springs back when touched.

Step 6

Remove the doughnuts to a wire rack, and immediately dip them in the cinnamon and sugar mixture, and place back on the wire rack to cool. Repeat until all batter is used.

Step 7

Serve when doughnuts have cooled. Enjoy