Preheat the oven to 350°F (175°C) and grease a donut hole pan.

In a mixing bowl, whisk together the dry ingredients: flour, baking powder, baking soda, salt, and sugar.

In another bowl, combine the wet ingredients: egg, buttermilk, melted butter, lemon juice, and lemon zest.

Pour the wet ingredients into the dry ingredients and mix until just combined. Gently fold in the blueberries.

Spoon the batter into the prepared donut hole pan, filling each cavity about 2/3 full.

Bake in the preheated oven for 10-12 minutes, or until a toothpick inserted into the center comes out clean.

Allow to cool in the pan for a few minutes before transferring to a wire rack to cool completely.