Preheat oven to 350°F, spray donut pan(s) with non-stick cooking spray and set aside
Whisk together the flour, brown sugar, salt, and baking powder in a large bowl and set aside
In a separate bowl, mix together the melted butter, yogurt, and egg until well combined. Stir in the lemon juice and lemon zest
Gently fold the wet ingredients into the dry ingredients until a dough forms (do not overmix, the dough will be very thick)
Gently fold in the blueberries into the dough until well distributed throughout
Spoon the dough into the donut pan(s) and smooth out gently
Bake 22-25 minutes, until a toothpick comes out clean
Cool in the pan for a few minutes, then turn out onto a cooling rack to cool completely
While the donuts cool, make your glaze. In a small bowl, mix the powdered sugar, lemon juice, and lemon zest together until a thick liquid forms.
When the donuts are cooled, dip the top half of each donut into the glaze and place back on the rack to allow the glaze to set*