Preheat your oven to 180°C (350°F) and line a 9x5-inch loaf pan with parchment paper. In a large mixing bowl, mash the ripe bananas thoroughly with a fork or potato masher until smooth.
Add the melted butter, eggs, granulated sugar, brown sugar, vanilla extract, and Greek yogurt. Whisk vigorously until smooth and well combined.
Sift the flour, baking soda, and kosher salt directly into the wet mixture. Mix with a spatula until almost combined.
In a small bowl, mix the melted butter, brown sugar, and ground cinnamon until it forms a cohesive mixture for the cinnamon swirl.
Pour half of the banana bread batter into the prepared loaf pan. Spoon the cinnamon mixture over the batter and gently swirl with a knife.
Add the remaining batter, and smooth it out with an offset spatula. Bake at 180°C (350°F) for 50–60 minutes, or until a toothpick inserted into the center comes out clean.
Let the banana bread cool completely in the pan for at least 30 minutes before removing.
While the bread cools, make the frosting by beating the softened cream cheese and butter together until smooth. Add the powdered sugar, vanilla extract, and a pinch of salt, beating until light and fluffy. Spread or pipe over the cooled loaf.