Preheat oven to 350 degrees F. Line an 8-by-8-inch square baking pan with parchment paper; generously butter parchment.
In a bowl, whisk together flour, salt, and baking soda until evenly distributed and set aside.
In a large mixing bowl, combine melted butter and brown sugar and mix until smooth and paste-like.
Mix in egg, followed by mashed banana and vanilla, mixing well until smooth.
Add dry ingredients and mix until just incorporated.
Stir in chocolate chips and pecans.
Pour into prepared baking pan, spreading into an even layer.
Bake for 30 to 35 minutes or until center is set and edges are light golden brown, and a toothpick inserted near the center comes out clean.
Place pan on a wire rack and let cool completely before lifting out and cutting into squares.
Blondies will keep in an airtight container for up to 5 days.
