Preheat your oven to 350°F (175°C) and grease your loaf pan with a bit of butter or cooking spray.

In a mixing bowl, peel the ripe bananas and mash them thoroughly with a fork or a potato masher until they're smooth. Set aside.

In another mixing bowl, melt the unsalted butter in the microwave or on the stovetop. Let it cool slightly.

Add the mashed bananas to the melted butter and stir well.

Sprinkle the baking soda and a pinch of salt over the banana-butter mixture, stirring it well. Allow it to sit for 2 minutes; it will start to bubble up.

Stir in the granulated sugar until it's fully combined with the mixture.

Add the beaten egg and vanilla extract, and mix until everything is well incorporated.

Gradually fold in the all-purpose flour until no streaks of flour remain, but be careful not to overmix. The batter should be just combined.

Mix the granulated sugar and ground cinnamon in a small bowl to create your cinnamon swirl mixture. Set it aside.

Pour half of the banana bread batter into your greased loaf pan.

Sprinkle about half of the cinnamon swirl mixture evenly over the batter in the pan.

Pour the remaining banana bread batter over the cinnamon swirl layer.

Sprinkle the remaining cinnamon swirl mixture on top.

Take a butter knife and gently swirl it through the batter to create a marbled effect. Don't overdo it; a few swirls will do.

Place the loaf pan in the preheated oven and bake for approximately 60 minutes. To check for doneness, insert a toothpick into the center of the bread; it should come out clean or with a few moist crumbs when it's done.

Once the banana bread is done, remove it from the oven and let it cool in the pan for about 10-15 minutes.

After it has cooled slightly, run a knife around the edges to loosen it from the pan and then carefully remove the bread from the pan. Place it on a wire rack to cool completely.

Once cooled, slice and serve! Enjoy your homemade banana bread with a delectable cinnamon swirl.