Preheat oven to 350.
Using a stand or hand mixer, beat bananas until they're fully mashed.
Add softened butter, vanilla, and sugar and continue mixing.
Beat in the egg.
Gradually pour in flour, mixing as you go.
Mix in baking soda and salt.
Mix in the Greek yogurt.
Pour batter evenly into well-greased Bundt cake pan and place pan in the oven.
Bake for about 45 minutes. Check bread with a toothpick; if the toothpick comes out clean, remove it from the oven and allow to cool for about 10 minutes before transferring bread from the Bundt cake pan to a platter.