Preheat your oven to 350 degrees F, grease or line a muffin tin, set aside.
In a large mixing bowl combine melted butter, sugar, eggs, and vanilla. Whisk well to combine. Add in the mashed bananas and gently mix to incorporate.
In a separate mixing bowl combine the flour, salt, and baking soda, mix to combine. Slowly add the dry ingredients into the wet until incorporated and smooth.
Use a portion scoop or measuring spoon to fill each muffin cup, about 2/3rd's full. Do not overfill. Bake at 350 for 22-25 minutes, or until a toothpick inserted in the middle comes out clean. Serve warm with soft butter or cool completely and store in an airtight container.