Mash the banana, then measure out ¼ cup.
In a bowl, whisk the banana, melted vegan butter, brown sugar, and vanilla extract until combined and fluffy (about 1 minute).
Add the flour, baking soda, and cinnamon and stir until a soft dough forms. DO NOT OVERMIX.
Let the dough rest for 10 minutes. While it rests, preheat oven to 350°F and line a baking sheet with parchment paper.
Scoop dough using a 1 tablespoon scoop and place on the baking sheet.
Bake for 11 minutes, until the edges are lightly golden and the centers are soft. these will look underbaked but will set as they cool.
Let cool before transferring to a rack.