Preheat oven to 350º F. Line a 10x15-inch jellyroll pan with parchment paper. (or foil sprayed with cooking spray).
Combine flour, 1/2 cup sugar, and salt in a large bowl. Cut in 1 cup of butter until it resembles coarse crumbs. Sprinkle the mixture into the prepared pan and press in firmly to make a crust. Bake in the preheated oven for 20 minutes.
While the crust bakes, add the corn syrup, brown sugar and 1/2 cup of white sugar, eggs, melted butter, and vanilla to a large bowl and mix until smooth. Stir in chopped pecans then spread filling evenly over the hot crust immediately after removing it from the oven.
Bake until filling is set, about 30 - 40 minutes. Allow to cool completely in the pan on a wire rack. Slice into bars, serve and enjoy!