Preheat oven to 350 degrees F. For crust, in a medium bowl combine flour, powdered sugar, and salt. Using a pastry blender, cut in the 1/2 cup butter until mixture resembles coarse crumbs. Pat crumb mixture into an ungreased 11x7x1-1/2-inch baking pan. Bake for 20 minutes or until lightly browned.
Meanwhile, for filling, in a medium bowl stir together eggs, pecans, 1/2 cup brown sugar, the corn syrup, 2 tablespoons melted butter, and vanilla. Pour over the baked crust, spreading evenly.
Bake for 20 minutes more or until the filling is set. Cool completely in pan on a wire rack. Cut into bars. Cover and store in the refrigerator.