Preheat oven to 350 degrees
In a bowl, mash up the bananas.
Add the apple sauce, egg, vanilla, flour, baking powder, baking soda and the pinch of salt. Mix until combine.
Pour in the blueberries and carefully fold into the batter with a spatula.
Spray a 9x9 square baking dish with cooking spray and pour in the batter.
Sprinkle the remaining blueberries on top of the batter and bake for 35-45 minutes or until a toothpick comes out clean.
Once out of the oven spray with the butter and let cool.
While the bread is cooling, in a bowl combine the yogurt, lemon zest, lemon juice and confectioners' sugar and drizzle over the bread or use as a dipping sauce.