Preheat your oven to 375 degrees F.
In a large mixing bowl, combine all of your dry ingredients (not blueberries) and stir.
In a medium size mixing bowl, combine all of your wet ingredients (aside from blueberries), and whisk.
Slowly mix your wet ingredients in with your dry. Stir until combined.
Gently fold in your blueberries. Gently! They will burst if it is not gently.
Using any left over melted butter (I scrapped the bottom of the bowl I used to heat it up) or using canola oil, lightly grease the donut tray.
Fill each donut mold evenly, with the mixture coming right to the top (see picture above).
Cook for 10-12 minutes, or until you can insert a toothpick with it coming out clean.
While donuts are baking, place all ingredients for frosting (other than the extra zest for topping) into a bowl and whisk until smooth! It will be drippy.
Let donuts cool for 30 minutes before frosting. To frost, simply dip them upside down into the bowl of frosting. Top with lemon zest!