Heat oven to 350°. Prepare four mini loaf pans (5.75" x 3") by spraying with cooking spray. Set aside.
In the bowl of a stand mixer, or use a mixing bowl with a handheld mixer, beat together the butter and granulated sugar until fluffy and combined. This takes about 1-2 minutes.
Add in the eggs and beat just until combined. Add mashed bananas, lemon zest, and lemon juice. Beat until combined and use a spatula to scrape down the sides.
In a separate bowl, add the all-purpose flour, baking powder, and salt. Stir with a whisk. Add flour mixture into the mashed banana mixture and gently stir with a spatula just until combined.
Gently stir in the fresh blueberries using a spatula.
Fill each loaf pan about ¾ of the way full and even out the top. Bake for 30-38 minutes.
Let the bread cool in the pans for about 30 minutes. Remove the bread from the loaf pans to glaze.
TO MAKE THE GLAZE: Stir together the powdered sugar, milk, and fresh lemon juice with a whisk. Add more or less milk/powdered sugar to reach desired consistency. You can either use a fork to drizzle the glaze on OR put the glaze into a Ziploc bag and cut the corner off and then glaze the bread for straighter lines.
