Break apart the bananas with your hands as you place them into a small saucepan. Add the other ingredients and place over low heat. Stir with a whisk to begin to break up the bananas.

Cook for about 15 minutes, continuing to whisk until the mixture is smooth and the bananas are mostly broken down. Remove from heat. Depending on the ripeness of your bananas, your whisk may be enough to create a smooth purée. Alternately, you can opt to use an immersion blender to create an ultra-smooth purée.

Transfer the banana butter to a pint mason jar and allow to cool to room temperature. Once cool, cover the jar with its lid, then label, date, and place in the refrigerator.