Prep the pan and oven. Heat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling for easy removal.

Whisk dry ingredients. In a large bowl, whisk the flour, baking soda, salt, and 2 teaspoons of cinnamon. This helps prevent clumps and keeps the crumb tender.

Mix the wet ingredients. In a separate bowl, mash the bananas until mostly smooth. Whisk in the granulated sugar, brown sugar, eggs, melted butter, yogurt (or sour cream), and vanilla until combined.

Combine gently. Pour the wet mixture into the dry ingredients. Stir with a spatula until just combined. A few streaks of flour are fine. If using nuts or chocolate chips, fold them in now.

Create the cinnamon ribbon. In a small bowl, mix the remaining 1/2 teaspoon cinnamon with 1 tablespoon sugar. Spread half the batter into the loaf pan. Sprinkle the cinnamon-sugar mixture evenly on top. Add the remaining batter and smooth the surface.

Top for crunch (optional). Sprinkle the top with turbinado sugar or a light dusting of cinnamon-sugar for a gentle crust.

Bake. Place the pan on the center rack and bake for 55–65 minutes. The loaf is done when a skewer inserted in the center comes out with a few moist crumbs but no wet batter. If the top browns too quickly, tent loosely with foil during the last 15 minutes.

Cool properly. Let the loaf cool in the pan for 10–15 minutes. Lift it out using the parchment and transfer to a wire rack. Cool at least 45 minutes before slicing to set the crumb.

Serve. Slice thick and enjoy plain, with butter, or warmed slightly. It’s excellent toasted the next day.