Prep your pan and oven: Heat the oven to 350°F (175°C). Line an 8-inch square pan with parchment paper, leaving overhang for easy lifting. Lightly grease the sides.
Mash the bananas: In a large bowl, mash the bananas until mostly smooth with a few small lumps.
You should have about 1 1/3 cups.
Whisk in the wet ingredients: Add tahini, maple syrup, oil, eggs, vanilla, and Greek yogurt. Whisk until the mixture looks smooth and creamy. The tahini may thicken it slightly—that’s perfect.
Combine dry ingredients: In a separate bowl, whisk together whole-wheat pastry flour, all-purpose flour, baking soda, baking powder, salt, and cinnamon.
Bring it together: Add the dry ingredients to the wet.
Stir gently with a spatula until just combined. Do not overmix. If using chocolate chips or nuts, fold them in now.
Fill the pan: Scrape the batter into the prepared pan and smooth the top.
Sprinkle sesame seeds or a few extra chocolate chips on top if you like.
Bake: Bake for 28–34 minutes, until the top is set and golden and a toothpick inserted in the center comes out with a few moist crumbs.
Cool: Let the cake cool in the pan for 15 minutes. Lift it out using the parchment and cool on a rack. Slice once it’s just warm or fully cool.
Serve: Enjoy plain, with a dollop of yogurt, or a light drizzle of honey.
It’s also great chilled the next day.