Preheat the oven to 350F.
In a small bowl, combine the ground flaxseed and water. Set aside to thicken.
In a large bowl, break the bananas into smaller pieces and mash them with a fork until they are smooth and creamy.
Next, add the brown sugar, orange juice, yogurt and flaxseed mixture. Stir to combine.
Add the cinnamon, ground nutmeg, salt and sunflower seeds and stir to combine. Next, gently stir in the flour and the baking powder and mix until everything is combined (be careful not to overmix).
Grease a loaf pan and scrape in the dough. Sprinkle extra brown sugar, a little cinnamon and some sunflower seeds on top.
Bake in the middle of the oven for 45-60 minutes, or until the banana bread is baked through (I usually use a pin to stick into the bread, if the pin comes out clean, the bread is ready).
Let the bread cool in the pan for 20 minutes, turning it on the side as it cools. Then remove from the pan and let it cool on a cooling rack.