Preheat the oven to 400F/200C, and line a 12-muffin baking pan with muffin liners.
In a large bowl, combine the all-purpose flour, salt, baking powder, and baking soda. Stir until the dry ingredients are well combined.
In a separate bowl, mash the ripe bananas using a fork. Whisk in the brown sugar, eggs, melted butter, milk, and vanilla extract until the wet ingredients are thoroughly mixed.
Create a well in the center of the dry ingredients mixture. Pour the wet banana mixture into the well. Gently mix the ingredients until everything is well combined and no lumps remain.
Fold in the chopped pecans or walnuts into the batter, distributing them evenly.
Using an ice cream scoop or a spoon, divide the muffin batter into the prepared muffin pan, filling each cup about two-thirds full.
Bake the muffins in the preheated oven for approximately 25-30 minutes or until the tops turn golden brown and a toothpick inserted into the center of a muffin comes out clean.
Once baked, allow the muffins to cool in the pan for about 5 minutes. Then, carefully transfer them to a wire cooling rack to cool completely.