Preheat the oven to 350 degrees F (175 degrees C). Lightly grease a 10x15-inch jellyroll pan, or line with parchment paper.
Combine flour, 1/2 cup sugar, and salt in a large bowl. Cut in 1 cup butter until mixture resembles coarse crumbs. Sprinkle mixture evenly over the prepared pan; press firmly to form a crust. Bake in the preheated oven for 20 minutes.
Meanwhile, mix corn syrup, 1 ½ cups sugar, eggs, 3 tablespoons melted butter, and vanilla extract together in a large bowl until smooth. Stir in pecans; spread filling evenly over hot crust.
Bake in the preheated oven until filling is set, about 25 minutes. Allow to cool completely in the pan on a wire rack before slicing into bars.
