Preheat oven to 350 F. Add a little extra avocado oil to grease the baking dish. Lay a piece of parchment paper, slightly smaller than the width, from one side of the dish to the other, leaving the ends hanging out. This way, you can easily lift the banana bread out once it's cooled.
In a medium-sized bowl, stir together the chia seeds and lukewarm water. Let it sit for 15 minutes.
In a large bowl, using a stand mixer or a whisk, beat together the bananas, oil, sugars, tahini and vanilla until smooth.
Add in the chia egg once it's ready and beat once more to combine.
In a separate bowl, stir together the flour, baking powder and salt.
Slowly add the dry ingredients to the wet ones, being careful not to overmix.
Once the batter is formed, pour it evenly into the baking dish. Top with the sesame seeds.
Place in the middle rack of the oven for ~50-55 minutes. Insert a toothpick into the center to check that it comes out clean, so you know it's ready.
Remove from the oven and place on a heat-proof surface to let it cool for 15 minutes.
Using the hanging edges, carefully lift the banana bread and remove it from the pan. You can place it on a silicone mat or another flat surface to cut it into even slices.
Enjoy right away, or store in an airtight container! Let it cool completely for another 30 minutes before locking it into a container.