Preheat your oven to 350°F. Grease a 9×9-inch baking pan with a little coconut oil and dust with flour to prevent sticking.
In a large bowl, whisk together the whole wheat flour, baking powder, baking soda, and sea salt.
In another bowl, mash the bananas until smooth. Stir in the coconut sugar, applesauce, eggs, Greek yogurt, and vanilla extract until well combined.
Gently fold the banana mixture into the dry ingredients, just until incorporated.