Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or grease the cups.
In a large bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until well combined.
In a separate medium bowl, mash the ripe bananas with a fork until smooth.
Add the granulated sugar, beaten egg, vegetable oil, and vanilla extract to the mashed bananas. Stir until combined.
Pour the banana mixture into the dry ingredients and gently fold together with a spatula until just combined. Do not overmix; the batter should be slightly lumpy.
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 let them cool in the tin for 5 minutes.
Transfer the muffins to a wire rack to cool completely before serving.