Preheat your oven to 350°F (175°C). Grease a loaf pan.
In a mixing bowl, combine mashed bananas, melted butter, and sugar. Mix well.
Add beaten eggs and vanilla extract to the banana mixture. Stir until combined.
In another bowl, whisk together gluten-free flour, cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in chocolate chips if using.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 60 minutes or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.