preheat oven to 350F. line an 8X8 or 9X13 baking pan with parchment paper, leaving 1-2 inch overhang (easy removal).
in a bowl, whisk together flour, baking soda and powder and salt. set aside.
stir well to combine brown sugar, tahini and melted butter.
add eggs and mix until glossy.
add in mashed bananas, yogurt and vanilla extract. mix until smooth and well combined.
add dry ingredients to the wet 1/2 at a time, stirring each time until JUST combined. you may still have a couple of white streaks.
pour batter into prepared baking pan.
bake at 350 F for 35-40 minutes, or until a toothpick inserted into the middle comes out mostly clean. for 9X13 start checking around minute 18-22 minutes.
cool in pan on a cooling rack for 30 minutes. remove bread from the pan using the parchment overhangs and cool on cooling rack an additional 15-30 minutes. top with tahini butter cream and crushed walnuts.