Preheat the oven to 375F.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda, cinnamon, and salt.
In a separate bowl, whisk together the yogurt, mashed banana, egg, oil, and vanilla.
Pour the yogurt mixture into the flour mixture and mix until just combined.
Pour the batter into a greased 8 inch square baking dish.
Bake for 25-30 minutes, until a toothpick inserted in the center comes out clean.