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In a large bowl, combine all-purpose flour, baking soda, baking powder, granulated sugar and salt.
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In another bowl, combine buttermilk, egg, oil, vanilla extract and lemon zest. Add buttermilk mixture to flour mixture and whisk until just combined (do not overmix).
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Spoon the batter into oiled non-stick doughnut baking tin sprinkled with dry bread crumbs (to prevent mixture sticking to the tin). Bake for about 20 minutes in the 350 F (175 C) preheated oven, or until a toothpick inserted into donut comes out clean. If you're using fresh blueberries, donuts will be baked in 15-18 minutes.