In a large bowl, mix butter and sugar until fluffy and fully blended.
Add one egg at a time, vanilla, and ripe bananas into the batter and mix until fully blended.
Add all dry ingredients, mix until fully blended.
In a separate mixing bowl, toss blueberries in 1 Tbsp of flour so they are lightly coated. Fold blueberries into the batter. This step prevents the berries from sinking to the bottom of the loaf when baking.
Pour batter into a lightly greased loaf pan.