Preheat the oven to 350 degrees. Grease a 9x5 loaf pan.
In the bowl of a stand mixer, cream together the butter and sugar until light and fluffy. Beat in the egg and vanilla until well combined.
Combine the flour, baking powder, and salt in a small bowl.
Add the flour mixture a little at a time to the butter mixture, alternating with the buttermilk.
Fold in the blueberries.
Add your batter to the greased loaf pan and spread evenly
Bake for 50-60 minutes or until a butter knife inserted in the center comes out mostly clean. Cool in the pan for 20 minutes before transferring to a cooling rack or cutting board. Cool completely before glazing.
To make the glaze, whisk together the powdered sugar and milk. Add more milk if you'd like the glaze thinner.