Grease a 9x5 inch loaf pan thoroughly with oil or cooking spray, then line the bottom and sides with parchment paper for easy removal. Preheat your oven to 350°F while you prepare the batter—this ensures the oven reaches the proper temperature right when you're ready to bake, which helps the bread rise evenly.

In a large mixing bowl, whisk together the flour, protein powder, baking soda, baking powder, salt, and cinnamon until evenly combined. Whisking the dry ingredients prevents lumps and distributes the leavening agents and spices uniformly throughout the batter, which is crucial for consistent texture and flavor.

In a separate medium bowl, whisk together the mashed banana, Greek yogurt, maple syrup, oil, and vanilla extract until well combined and smooth. The yogurt adds moisture and protein while the maple syrup provides natural sweetness—whisking these together creates an emulsion that helps bind the dry ingredients smoothly.

Pour the wet ingredient mixture from Step 3 into the dry ingredient mixture from Step 2, then gently fold them together using a spatula or wooden spoon until just combined. I like to stop folding as soon as I don't see any streaks of dry flour—overmixing develops gluten and creates a dense, tough crumb rather than the tender, moist texture you want in quick breads.

Pour the batter from Step 4 into the prepared pan from Step 1, spreading it evenly with a spatula. Bake in the preheated 350°F oven for 40 minutes, until a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter). Then turn off the oven and leave the bread inside for 5 additional minutes—this gentle carryover cooking helps the center set without over-baking the edges.

Remove the bread from the oven and let it cool in the pan for about 10-15 minutes until it's comfortable to handle but still slightly warm. Run a thin knife around all four edges to loosen the bread from the pan, then flip it onto a serving plate or cooling rack. Let it cool completely before slicing—I find waiting at least 30 minutes helps the crumb structure set properly so you get clean slices rather than a crumbly mess.