Preheat your oven to 400° F. And prepare your donut pan(s) with non-stick spray (or butter and a little flour).
In a large bowl mix your flour, baking powder, baking soda and salt. Stir until well combined.
In a separate large mixing bowl whisk together your melted butter and sugar. Add one egg at a time into the mixture. Then add the vanilla, lemon juice and buttermilk. Whisk this until there are no more clumps.
Slowly add the dry mixture into the wet, whisking as you add.
Fold in your rinsed blueberries. You don't want to over mix and mash the berries.
Using a cookie scoop, spoon, or piping bag disperse the thick batter into the greased pans. The batter should be evenly distributed in the pan, but doesn't need to reach the top rim. See photos above for leveling.
Bake each set for 10 minutes. Let cool and remove to cooling rack.
As for the icing:
In a shallow bowl combine your sugar and zest. Slowly mixing in the milk tablespoon by tablespoon until you reach the right consistency. You want it liquidity enough to slightly drizzle over the side of the doughnuts.
Dip your cooled donuts face down into the bowl, remove and let them set on the cooling rack.