Preheat the oven to 375°F (195°C)
In a small bowl, combine the ingredients for the flax egg and set aside.
In a medium sized bowl, combine all of the dry ingredients. In a seperate bowl, combine all of the wet ingredients, including the flax egg.
Slowly pour the dry ingredients into the wet ingredients, whisking to combine. The batter should be thick. If it appears too thin, add 1 tbsp of gluten-free flour at a time until it thickens.
Fold in the blueberries
Lightly grease the donut pan with oil. Using a spoon or pastry bag, fill each donut opening until it is full to the top
Bake in the oven for 15-18 minutes or until a toothpick inserted into the center comes out clean.
Take the donuts out of the oven and let the donuts cool for 5 minutes in the pan. Then gently transfer the donuts to a wire rack to cool for 5-10 minutes.
Leave the donuts as is, or try topping them with the Blueberry Lemon Glaze!