Preheat oven to 350F and line an 8x8 baking dish with parchment.
In a bowl mix together tahini and honey, add enough water to make it drizzle, set aside.
Mash the bananas with beaten egg, sugar, vanilla and tahini (or blend all in a food processor, which is my method of choice).
Whisk together the flour, cocoa, baking soda, salt.
Mix the two until just combined (do not overmix).
Pour into the prepared pan, drizzle the topping on and swirl it around with a knife. Decorate with optional seeds if using.
Bake 20-25 minutes until a knife inserted to the bottom comes out clean.
Let the cake cool and slice into 9. Enjoy! Keep leftovers refrigerated or freeze!