Preheat your oven to 350°F (175°C) and prepare a 9x5-inch loaf pan by greasing and flouring it or lining with parchment paper.

In a medium bowl, whisk together the flour, baking soda, and salt, then set aside.

In a large mixing bowl, cream together the butter and brown sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Then mix in the Greek yogurt and vanilla extract until smooth.

Incorporate the mashed bananas, stirring until there are no large chunks.

Gradually add the dry mixture, stirring gently to avoid overmixing.

In a small bowl, combine the granulated sugar and cinnamon.

Pour half of the batter into the prepared loaf pan and sprinkle half of the cinnamon-sugar mix over the top.

Spread the remaining batter on top and finish with the remaining cinnamon-sugar mixture.

Using a butter knife, gently swirl the cinnamon mixture into the batter.

Bake in the preheated oven for 60-65 minutes, or until a toothpick comes out clean.

Let the bread cool in the pan for about 10 minutes before transferring to a wire rack.