Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or grease the cups.
In a large mixing bowl, mash the ripe bananas with a fork until smooth.
Add the granulated sugar, brown sugar, melted butter, egg, and vanilla extract to the mashed bananas. Stir until well combined.
In a separate bowl, whisk together the baking soda, salt, and all-purpose flour.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.
Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full.
Bake in the preheated oven for 18 to 20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove the muffins from the oven and allow them to cool in the tin for 5 minutes.
Transfer the muffins to a wire rack to cool completely before serving.