Start by preheating your oven to 350 F. Grease a donut pan by brushing butter in each donut cavity. Set aside.

Mix together in a medium bowl 1 cup of all-purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, 1/4 teaspoon of salt, and 1/4 cup of granulated sugar. Set aside.

In another bowl or a 2 cup measure cup, mix together 1 egg, 1/3 cup plus 1 tablespoon of milk, 2 tablespoons of oil and 1 teaspoon of vanilla.

Add to the dry ingredients along with the zest of 1/2 a lemon. Mix together until just combined.

You can either spoon the batter into each donut cavity or use a piping bag to do this. If you don't have a piping bag you can cut one of the corners off of a freezer bag. Fill the donut cavities about 2/3 full being careful not to overfill or you will end up with muffin tops instead of donut holes.

Now take your blueberries and press them into the batter, I like to use about 5 in each donut. Take a spoon and just cover up the top of the blueberries with the surrounding batter.

Bake in preheated oven for 9-10 minutes. Let cool for 5-10 minutes in the pan before removing onto a wire rack to cool completely.

Prepare the lemon glaze by whisking together 1 cup of icing sugar, 1 tablespoon of lemon juice, 1 tablespoon of milk and 1/2 teaspoon of vanilla extract until smooth.

Take the donuts and dip one at a time into the bowl of glaze and place them back on the rack to let the icing set. If you have extra icing at the end feel free to dip the bottoms of your donuts too!