In a large mixing bowl, mash the ripe bananas until smooth.
Add the granulated sugar, vegetable oil, milk, and vanilla extract to the mashed bananas and mix well until combined.
In a separate bowl, sift together the all-purpose flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.
Heat a non-stick skillet or heavy-bottomed pan over low heat. Lightly grease the pan with a small amount of oil or butter.
Pour the batter into the pan and spread it evenly.
Cover the pan with a tight-fitting lid and cook on low heat for about 20 minutes, or until a toothpick inserted into the center comes out clean.
Remove the pan from heat and let the cake cool slightly before removing it from the pan.
Slice and serve the banana cake warm or at room temperature.