Preheat the oven to 350°F (175°C) and grease a 9x9-inch baking pan with butter or non-stick spray.
Prepare the crust:In a medium bowl, mix the flour, powdered sugar, and butter. Use your hands or a pastry cutter to combine the butter into the dry ingredients until the mixture becomes crumbly.Press this mixture into the bottom of your prepared pan, ensuring it's evenly distributed. Bake for 15 minutes until golden brown, then remove it from the oven.
Make the pecan topping:While the crust is baking, melt the butter for the topping in a saucepan over medium heat. Add the brown sugar and stir until the sugar dissolves. Remove from heat and stir in the eggs, vanilla extract, and salt until smooth. Fold in the pecans.
Assemble the bars:Pour the pecan mixture evenly over the cooled crust. Spread it with a spatula to ensure it's even.Bake for 20-25 minutes, or until the topping is firm and golden brown. Let the bars cool completely before cutting them into squares.