Preheat your oven to 350°F (175°C) and prepare a standard muffin tin with liners or grease them.

In a large bowl, mash the ripe bananas, then mix in granulated sugar, brown sugar, vegetable oil, and vanilla extract until creamy.

Sprinkle baking soda, salt, and optional cinnamon over the wet mixture and fold in gently.

Add all-purpose flour and mix until just combined, without overmixing to keep muffins fluffy.

Fold in the chopped walnuts, distributing them evenly throughout the batter.

Spoon the batter into the muffin cups, filling them about two-thirds full.

Bake for 20-25 minutes until a toothpick comes out clean or with a few crumbs.

Allow the muffins to cool in the tin for about 5 minutes, then transfer to a wire rack to cool completely.