Preheat oven to 350°F (175°C). Grease a 9x5 inch loaf pan with coconut oil or line with parchment paper.
In a large bowl, mash the bananas with a fork, leaving some small chunks for texture. Whisk in the Greek yogurt, maple syrup, eggs, melted coconut oil, and vanilla until well combined.
In a separate bowl, whisk together the whole wheat pastry flour, baking soda, salt, and cinnamon if using.
Gently fold the dry ingredients into the wet ingredients until just combined. Don't overmix – some lumps are fine.
Pour the batter into the prepared loaf pan and smooth the top gently.
Bake for 50-55 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs.
Cool in the pan for 10 minutes, then turn out onto a wire rack to cool completely before slicing.
Notes
Storage tip: Wrap tightly and store at room temperature for up to 3 days, or slice and freeze for up to 3 months. The bread actually improves in flavor after the first day.