Preheat the oven to 350°F (175°C). Line a 9 × 5-inch loaf pan with parchment paper, leaving an overhang along the long sides, then lightly grease the parchment with cooking spray.

In a large bowl, whisk together the flour, sugar, salt, and baking soda.

In a separate medium bowl, whisk together the mashed bananas, eggs, buttermilk, melted butter, and vanilla extract.

Add the wet ingredients to the dry ingredients and stir just until combined. Avoid overmixing. Set the batter aside.

In a small bowl, whisk together the softened cream cheese, egg, sugar, and flour until smooth. A handheld mixer may also be used.

Spread about one-third of the banana bread batter into the prepared loaf pan.

Add alternating dollops of the cream cheese filling and remaining banana bread batter over the first layer.

Run a knife gently through the batter to create a cream cheese swirl without fully blending the layers together.

Bake for 50–60 minutes, or until the top is set and a tester inserted into the banana bread portion comes out with only a few moist crumbs.

If the edges begin browning too quickly, loosely tent the loaf with aluminum foil and continue baking.

Remove the bread from the oven and let it cool in the pan for 10 minutes.

Use the parchment overhang to lift the loaf from the pan and transfer it to a wire rack. Cool completely before slicing and serving.