The first step here is to make the blueberry reduction that will eventually become the blueberry glaze, since you want to let it cool for a little while. Place your blueberries, granulated sugar, and water into a small pot or saucepan. Heat on medium to bring it to a simmer, then let it simmer for around 5-7 minutes. During this time, use a spatula or spoon or fork to break up the blueberries.
Once there are no large chunks left, remove the pan from the heat and use a fine mesh strainer to strain out the liquid. You will get around 3-4 tablespoons of liquid. Set it aside to cool entirely while making the donuts.
For the donuts themselves, preheat the oven to 350°F and grease a donut pan. In a large bowl, mix together the gluten free flour, granulated sugar, baking powder, and salt. Then add in the milk, neutral oil, soda water, and vanilla extract. Mix until just combined.
Finally, add the blueberries into your batter. I go more in depth on this throughout the post, but doing ½ cup will really stuff the donuts with blueberries in a way that is delicious, but may leave them a little fragile, as it’s tougher for the donuts to hold their shape with that many bursting blueberries inside of them. So if you don’t want to run the risk of any donuts breaking in half, I’d recommend doing 1/3 cup instead.
Once the batter is ready, spoon it evenly across the 6 donut molds in the pan. Bake for 15 minutes, then let them cool entirely in the pan before flipping them out onto a cooling rack.
When the concentrated blueberry liquid is cooled and the donuts are cooled, it’s time to make the glaze. Simply mix the powdered sugar into the cooled blueberry liquid, adding a little at a time and mixing along the way until you reach your desired consistency. Then dip the donuts into the glaze adding as much as you want.
Eat and enjoy!