Preheat the oven:
Preheat your oven to 350°F (175°C). Grease or line a 9×5-inch loaf pan with parchment paper.

Mix the wet ingredients:
In a large bowl, mash the ripe bananas until smooth. Add the melted butter, granulated sugar, brown sugar, eggs, and vanilla extract. Stir until well combined.

Combine the dry ingredients:
In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, and cinnamon (if using).

Add the dry ingredients to the wet ingredients:
Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Be careful not to overmix.

Add sour cream or yogurt:
Stir in the sour cream or yogurt until the batter is smooth.

Toss the blueberries:
In a small bowl, toss the blueberries with the 1 tablespoon of flour (this helps prevent the blueberries from sinking to the bottom). Gently fold the blueberries into the batter.

Pour the batter into the pan:
Pour the batter into the prepared loaf pan and spread it evenly.

Bake the bread:
Bake for 60-70 minutes, or until a toothpick inserted into the center of the loaf comes out clean (or with a few moist crumbs). If the bread starts to brown too quickly on top, cover it loosely with aluminum foil and continue baking until done.

Cool and serve:
Let the bread cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely before slicing and serving.