Prep the pan and oven: Heat the oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment, leaving overhang for easy lifting, and lightly grease the sides.

Mash the bananas: In a large bowl, mash the bananas until mostly smooth with some small lumps for texture. You should have about 1 1/3 cups.

Whisk the wet ingredients: Add eggs, oil, yogurt, brown sugar, and vanilla to the bananas. Whisk until well combined and glossy. The mixture should look creamy.

Combine the dry ingredients: In a separate bowl, whisk the all-purpose flour, whole wheat flour, baking soda, baking powder, salt, and cinnamon.

Bring the batter together: Add the dry ingredients to the wet. Stir gently with a spatula just until the flour disappears. Do not overmix or the loaf will be dense.

Fold in extras (optional): If using nuts, chocolate chips, or berries, fold them in with a few strokes. Save a few to sprinkle on top if you like.

Fill the pan: Pour the batter into the prepared pan and smooth the top. For a classic bakery look, run a thin knife or spatula in a shallow line down the center.

Bake: Bake for 55–65 minutes, until the top is deep golden and a toothpick inserted in the center comes out clean or with a few moist crumbs. If the top is browning too quickly, tent loosely with foil for the last 10–15 minutes.

Cool: Let the loaf cool in the pan for 10–15 minutes. Lift out using the parchment and cool completely on a rack before slicing for the cleanest cuts.

Slice and serve: Use a serrated knife for neat slices. Enjoy warm, at room temp, or lightly toasted the next day.