Preheat oven to 350 degrees. Coat standard size donut pan with nonstick cooking spray. Set aside.

In a large bowl whisk together flour, 1 cup sugar, baking powder, baking soda, cinnamon, and lemon zest.

In a small saucepan melt butter over low heat. Set aside.

In a medium bowl, whisk together buttermilk, eggs, vanilla and melted butter for 2 minutes.

Pour egg mixture into flour mixture and mix until well combined.

Carefully fold in blueberries. Do not over mix.

Pour dough into gallon-sized ziploc storage bag.

Cut a 3/4 inch whole in bottom one corner of bag.

Pipe dough into donut molds filling 3/4 full.

Bake for 10 minutes or until donuts spring back when touched.

Remove from oven and let cool in pan for 5 minutes, then invert onto cooling rack.

Dip both sides of warm donuts into extra 3/4 cup sugar.