Preheat oven to 350° F.

Butter a 9- x 13-inch baking pan.

Combine flour, sugar, and salt. Add the butter to the flour mixture. With a pastry blender, cut in cold butter until mixture resembles very fine crumbs.

Press mixture evenly into the 9 X 13 pan. Bake 18 to 20 minutes or until lightly browned, rotating halfway through. While crust is baking, prepare the filling.

In a small bowl, beat eggs lightly. Combine brown sugar, granulated sugar, corn syrup, and 1/2 cup butter in a saucepan.

Bring to a boil over medium heat, stirring gently. Once the filling is brought to a boil, turn off burner and remove saucepan from heat.

Temper the eggs by slowly pouring about one third of the hot sugar mixture into beaten eggs. Stir the tempered egg mixture back into the remaining hot sugar mixture and mix well. Stir in pecans and vanilla.

Pour filling over crust. Bake at 350° for 30-35 minutes or until set.

Cool completely in pan on a wire rack. Once cooled, remove from the baking dish and slice into 1- x 1-inch squares.