Preheat your oven to 350°F (175°C) and grease a donut pan with non-stick spray or butter.

In a large mixing bowl, combine the all-purpose flour, sugar, baking powder, baking soda, and salt. Mix well to ensure all ingredients are evenly distributed.

In a separate bowl, whisk together the buttermilk, melted butter, egg, lemon juice, and lemon zest until fully combined.

Gradually pour the wet mixture into the dry ingredients. Stir until just combined; do not overmix.

Carefully fold in the blueberries.

Using a piping bag or a spoon, fill each donut mold approximately halfway with the batter.

Place the pan in the preheated oven and bake for about 10–15 minutes, or until a toothpick inserted into the center comes out clean.

Let the donuts cool in the pan for a few minutes before transferring them to a wire rack. Once cooled, drizzle with a lemon glaze made from powdered sugar and lemon juice.