Preheat the oven to 350 degrees F. Grease and flour a 9 x 5 baking pan.
Make the cinnamon swirl. Mix together the ingredients for the swirl together. Use your fingers or a fork to mash the butter into the dry ingredients until well-combined.
Melt your butter, allow it to cool slightly.
Mash your bananas.
Mix together your butter, bananas, eggs, yogurt, vanilla and sugar until well-combined.
In a separate bowl, mix together the salt, flour, cinnamon, and baking soda together.
Mix the wet and dry ingredients together. Only mix until just combined. There should still be some lumps.
Pour some of the batter into the loaf pan. Add in some of the cinnamon swirl. Continue this pattern until you've used both up. End with the banana batter.
Bake for 50 - 70 minutes, or until a toothpick comes out clean. If the top begins to brown too fast, lightly top with aluminum foil.
Allow to cool for a few minutes before removing from the pan to cool completely.
Notes
Wrap the banana bread tightly in plastic wrap when fully cooled.