Meanwhile, make the filling. In a stand mixer fitted with paddle attachment, add the butter, brown sugar and a pinch of salt and mix on medium speed until light and fluffy, about 3 minutes. Add the corn syrup, flour, and pecans and mix until just combined. Spread the filling over the baked crust and bake until golden brown, about 30 to 35 minutes. Remove the dish from the oven and allow it to cool completely in the pan.