Preheat oven to 350. Lightly spray donut pan with non-stick cooking spray.
In a bowl, stir together flours, sugar, baking powder, salt, and lemon zest. Set aside.
In a small bowl, whisk together lemon juice, buttermilk, egg, melted butter, and vanilla extract.
Add wet ingredients to dry ingredients and stir until just combined. Gently fold in blueberries.
Using a pastry bag or a plastic bag with the tip cut off, pipe batter into prepared donut pan. Fill about ⅔ full. (I think it's easier to spoon the batter into the donut molds, but that's just because I'm lazy!)
Bake for 10-12 minutes or until edges of donuts just start to turn golden brown.
Remove from oven to a wire rack to cool for 5 minutes before removing from pan.
Repeat until batter is gone.
While donuts are cooling, stir together all glaze ingredients until smooth.
Dip cooled donuts in glaze. Allow glaze to harden before serving.
While these donuts are best served fresh, leftovers can be stored in a loosely covered container. (We found that they were definitely best the day-of!)