Preheat the oven to 350°F and grease a donut pan and set aside.
Whisk together the flour, sugar, salt, baking powder, and cinnamon in a large bowl and set aside.
In a measuring cup or small bowl, whisk together the buttermilk, eggs, vanilla, and melted butter.
Combine wet ingredients with dry until just combined with a rubber spatula, then fold in blueberries.
Transfer the donut batter to a disposable piping bag and pipe into the greased donut pan circling twice to fill (about ⅔ full). Tap the pan on a countertop or table to evenly distribute the batter.
Bake for 15 to 18 minutes. Allow donuts to cool for 5 minutes in the pan and then invert onto a cooling rack to fully cool!
Prepare the glaze while donuts are cooling. In a medium deep bowl, whisk together powdered sugar and mashed blueberries.
Dip the tops of the donuts in the glaze and return to a cooling rack with a cookie sheet underneath to set. Garnish with sprinkles and additional blueberries if desired!