Preheat oven to 350F and spray an 8X4 loaf pan with non stick spray and set aside.
In a medium bowl, sift together flour, baking powder, and salt. Set aside. In a small bowl, mix fresh washed blueberries and cornstarch until blueberries are fully coated. Set aside.
In a medium bowl, cream together butter and white sugar for 2 minutes. The butter will be very light in color and fluffy. Add in lemon juice, lemon zest, and vanilla. Add in eggs one at a time. Add in ⅓ of dry ingredients, then ½ of the butter milk and repeat until ending on dry ingredients. Gently fold in blueberries. Pour batter into loaf pan.
Bake bread for 50-60 minutes. The bread is finished when golden brown on the top and when a toothpick is inserted it comes out clean. Let sit in pan for 10 minutes. Then remove bread to cooling rack.
When bread is completely cool, glaze the top. In a small bowl add the milk and slowly add the powdered sugar and whisk. The glaze should be thick and easily pourable. Add in the powdered sugar one tablespoon at a time until desired consistency is reached. Pour glaze over the top of bread. Keep in fridge until ready to serve.